Because it's low effort and cheap which shows a lack of creativity and talent.
Majority of the time it cannot stay on model and people defend that for some reason
It blends together with everything else being released
Basically it comes down to the entirety of making animation was overtaken by people who have no skill at making animation.
That isn't to say this style couldn't be used well, but it's being used poorly. Look at the Classic Disney style, other people tried to replicate it and very few succeeded in making something that didn't move and look like crap.
The people using this style do not care one bit about the craft.
It is the animation style equivalent of taping a banana to the wall and calling it art and then getting confused when people begin debating if the entire concept of art even has value besides as a meme.