Man I hate these .1 chapters, why can't they be released as a full chapter
Shrinkflation and the general enshitification of anything that can be monetized at large. The manga we consume has largely moved to an online distribution model, rather then scanning from a physical magazine. So the publishing website can distribute more chapters with fewer pages which in turn means more eyeballs on their website, and more ad revenue.
They can also encourage subscribers to check in more often for daily/weekly uploads of chapter parts whereas before it would have been longer intervals between full chapter releases.
So yeah, it's all about money and trying to keep as much of audience focused on their products while squeezing out enough money to satisfy the perent companies and their investors.