They weren't all on the same continent, The Aztecs and Maya lived in North America, the Inca and the Tupi in South America. The Aztec Empire barely reached the borders of the various Maya kingdoms and therefore their contacts with them were mostly relegated to trade since there were nearer kingdoms for the Aztecs to fight. The Incas were on the other side of South America from the Tupi, and it's a very large continent. There's the Andes and the Amazon rainforest between them, it's basically like asking why didn't Portugal and Poland wage war on one another throughout the Middle Ages.

Some other things to remember:

• The Inca were a small ethnic group from southern Peru that embarked on a massive diplomatic and military campaign in the 15th century. Their full empire, as we know it, barely lasted 100 years. This involved plenty of battles; the Chimu in the north and the "Che" in the south put up quite a fight. The "Che"/Mapuche in Chile wouldn't be absorbed into another state for decades. The Inca also represent the tiniest sliver of Andean history. Warfare was frequent for the 1000 years of life in the Andes beforehand. You can read a recent post from me about how embedded warfare was in Recuay life, a people group from the first few centuries AD, and they were hardly alone. We just never hear about these because high school world history books are awful because... actually, never mind, I can't think of a legitimate reason besides that for why people shouldn't know more about the very continents they live on.

• The Maya weren't a "civilization" in the same sense as the single, unified Inca and Aztec empires. They were a number of powerful, competing city states with a shared culture. Sometimes the city of Tikal and its allies were on top, sometimes it was Calakmul. Power frequently shifted, and that more often than not involved warfare, capture, and sneaky political manipulations.