This is a difficult question to answer, whether there should be more attention paid or not. The answer obviously has to be subjective by the nature of the question.

There actually is some really good scholarship, though. There are a couple minor issues though. To start, it's only recently that a lot of the local Qing-era sources have become available. Many are still simply not yet translated into anything other than Chinese. This means that if you're going to produce anything in English, you're either required to be able to read and have access to the Chinese sources, or you're going to have to rely on Chinese language sources.

Still, that doesn't mean it's not happening.

Some good examples are The Secret History of the Hakkas: The Chinese Revolution as a Hakka Enterprise by Mary Erbaugh (1992) which talks specifically about the role Hakka people have played in China's history. Not just people like Deng Xiaoping or Hong Xiuquan, but also the network of Hakka members of secret organisations like the Heaven and Earth Society and the role they had in trade and military throughout the 19th century. It was these secret societies and the various native-place associations (同鄉會) that formed the backbone not only of trade but also intelligence networks throughout Southeast Asia at the time.

In Chinese you also have the works of Luo Xianglin 羅香林 who is considered the father of Hakka studies. He was writing in the 1930s (most famously with《客家源流考》) against the backdrop of marginalisation of the Hakka throughout South China at the end of the Qing and start of the Republic.

This was a time after the Hakka-Punti Clan Wars which would be a long thread all on it's own. The important point is that it was a period in the middle of the century where, due to resentment built up by migrations and a complex system of land ownership moving wealth into the hands of new arrivals at the cost of the established "native" population, tensions reached such heights that war broke out in China and the Malay Peninsula which affected relationships in the region for generations to come. By the time Luo Xianglin was writing, anti-Hakka sentiment had been codified in official texts as part of Qing efforts to reform education by encouraging local gazetteers as the first step to teaching the youth to love the country.

Luo Xianglin's work was a response to this, and has informed Hakka studies up to the present, outdated as some of his points may be. Still, he documented and mapped out waves of migration and towns of origin and provided the first well-distributed history. He wasn't the first, but he was up to that point the most successful.

Much more recently there's the work of the late Sow-Theng Leong, Migration and Ethnicity in Chinese History: Hakkas, Pengmin and their Neighbours which goes into phenomenal detail about the history of the Hakka specifically as a migrant people and the pressures they faced in the most notable period of their history up through the 19th century. Leong's work was published in 1997 and I have yet to see a more detailed account in English out there since, and not for lack of trying.

So like I said, it's hard to answer the question of should there be more. But at least we can say there's been more coming out, and we can almost certainly expect even greater scholarship in the coming years as more work gets translated and more records begin to surface. Maybe then the significance of the Hakka as a people will be more fully recognised in the West.

Hopefully that at least somewhat answers your question. I for one am glad to see more people asking about the history of the Hakka here.

Also, if anyone is curious, I've also written an overview here in response to the question Who are the Hakka people of China?. There's also a little bit here that I've written about the backdrop of the 19th century and how it propelled migrant work abroad.