Another reason is that they mean what they say... That they really, really hate the style of writing, enough to fixate on that.
Personally, I think the people whining about the style are silly. Maybe because I'm terrible at grammar and spelling, but I always just focus on the message, not the delivery. I just care about the concept, facts, the argument, and so forth. The actual grammar and spelling are just trees, while the forest is the point.
Edit: just an infobit: The reason my text isn't full of errors is due to the awesomeness of the dictation and a custom hotkey I have created on my computer, which uses a local LLM to spellcheck any text I have selected and replaces it with the corrected one. Nothing has improved my quality of life and writing more than these two tools!