Great question!

The simple answer is that Hawaii was not really on the route taken by Spanish galleons as they crossed the Pacific. The Galleons followed a track much closer to the equator when heading from the Americas. Then, running from the Philippines, the galleons sailed far to the north of the Hawaiian archipelago. So the islands were not a natural stopping point for the Spanish in the same way as Guam. Beyond that, the Spanish were rarely interested in exploring much of Oceania (or funding exploration at any rate) and suffered a series of failures during the brief time in which they seemed poised to consider expansion into Oceania.

While the galleon trade drove Spanish expansion on either side of the Pacific, it did not inspire any sustained program to expand within it. After all, the point of the galleons was to ride the natural wind cycle between the Americas and Asia for the purpose of trade. The galleons were not built to be ships of exploration.

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The Spanish occasionally showed an interest in exploring and expanding into Oceania, primarily in the late 16th and early 17th centuries. However, they largely met with resounding failure, which might also help explain why they did not, and likely could not, have expanded to Hawaii.

Alvaro de Mendaña y Neira led two attempts to establish a Spanish presence in the Pacific, first in 1567 and then again in 1595. Inspired by a religious revelation that the wealth of King Solomon might be in the Pacific (or at least an equivalent wealth to what had been secured in the Americas), Mendaña secured help from his uncle, the Spanish authority in Peru to lead an expedition into the Pacific. The expedition reached the Solomon Islands, where it landed on an island they anointed Santa Ysabel. The island turned out to be anything but the sparkling and wealthy lost continent the Spanish navigators had hoped to find. However, the island was a source of salvation for the crew, who suffered scurvy and poor health. The Spanish offered trade, promises, and threats to gain food, primarily pork and root crops like taro, from local peoples.

The situation grew tense as the Spanish recovered their health. The local population knew nothing of gold and lost Kingdoms, did not have sufficient surplus agricultural production to sustain the Spanish, and seemed uninterested in religious conversion. Eventually, fighting broke out between the Spanish and Solomon Islanders-- Spanish firearms proved ineffective in the tropical environment (and were hardly accurate anyway). The outnumbered Spanish eventually fled back to Peru.

Mendaña never gave up the dream, though. About thirty years later, the crown agreed to allow him to lead a second expedition. This time he reached the Marquesas (which sit much closer to the galleon path than Hawaii). As the Spanish approached the shore, ships came out to meet them with food and goods-- the Spanish understood the goods as tribute or a holy offering rather than the first part of a reciprocal exchange in which permission to land is given, and violence broke out. Alvaro led his men and ships away from the Marquesas Islands and reached the Solomon Islands again. They landed on a different island called Santa Cruz and declared a new holy colony, Graciosa Bay. The pattern of Mendaña's prior encounters in Oceania repeated itself. The Spanish needed goods while they set themselves up, local populations provided that to a point, and then relationships broke down. Violence began as Spanish demands were not met, and threats were issued. After about a month, Mendaña and a sizeable contingent of his men had died from endemic malaria and fighting. His wife, Dona Isabel, took command and ordered the survivors to sail for home.

Pedro Fernandes de Queirós launched another expedition to expand Spanish influence in Oceania in 1605. He followed the route of Mendana for the Solomon Islands but landed at Vanuatu instead. He believed he had discovered an earthy paradise and decreed his colony to be New Jerusalem. He envisioned a grand city of white marble laid out in a cross pattern. However, his crew was suffering from scurvy and poor nutrition. Relations with local peoples were poor from the beginning. Ultimately, the Spanish were forced to retreat from the island again.

The Spanish were more successful in their conquest of the Marianas Islands, including the valuable stopover on Guam. However, that conquest came at a massive price. The death of several catholic missionaries on the islands in the late 1660s precipitated near constant low-level warfare between the Spanish and Chamorro during the 1670s. Local Spanish authorities constantly requested Spanish and Filipino soldiers be sent to help maintain order. However, even those troops proved troublesome, and several mutinies occurred during the 1680s. For instance, in 1684, as the Spanish forces spent much of the year under siege in their fort at Hagåtña, soldiers began to plot a mutiny (or mass desertion) against the Spanish administrators and friars. The Chamorro encouraged them to switch sides and relayed that they had no issue with the soldiers, just the Spanish authorities. Ultimately the mutiny fizzled when Spanish relief forces arrived from elsewhere in the archipelago-- Spain had been forced to withdraw from the other islands of the archipelago and concentrate forces on relieving Hagåtña. It took until 1698 before Spain managed to exercise control on the islands and forcibly relocated a great deal of the population into new villages and administrative regions.

The Spanish were successful on Guam because they could call upon reinforcements from the Philippines. This was not an option during some of the earlier attempts at expanding into the Pacific. It also took Spain over a hundred years from Miguel Lopez de Legazpi's first territorial claim over Guam in 1565 to 1698, when Spain could finally be said to have solidified its conquest of the island. Even with the nearby support in the Philippines (where the Spanish faced other challenges/challengers), conquest was not so simple.

Considering that Hawaii was not on the typical track of the galleons and the failures Spain suffered elsewhere in the Pacific, expansion was not high on the priority list. It simply was not necessary to maintain the galleon circuit.