Creating a list of "Best Budget Streamers with Built-in DAC" is like creating a list of best budget turntables with built-in phono preamplifiers. They exist, and people buy them. But they are the best of the worst.
I think it’s a question of preferences and personal circumstances. In the same way as turntable with built-in phono stages and also integrated amps, people who buy them usually value their small footprint and convenience.
In the case of budget products, in some cases, it’s a way for some people to start their hi-fi journey and the goal here is to make sure that these people access the best possible price/performance ratio. Once they get a taste for it, they might further down the line invest in separates. In the same way as a turntable with built-in phono, people start with these as they are accessible and easy to use and once they get more serious about it, they might invest in an external phono preamp.
The higher-end you go the less integrated the products are anyway, with the exception maybe of integrated amps, with now very high-end models as manufacturers understand that some people like their convenience.