English is not my native language. This means that I will commit grammatical errors at some point. Like most people here, I am an amateur who strives to be a better writer over practice and time. So, why do "so many writers" use bad grammar? Because we all make mistakes, and if we are directed towards it in a constructive manner, we learn not to do it again in the future.
... I think you have a grammatical error in your bio. There's an "i" in minuscule whereas it should be in majuscule. You're welcome. :)
"More people will read what you have written, if you edit better before publishing."
A valid point, but it's non-constructive and even offensive to some. It won't help these writers because you are not giving the details. Where are the errors? Direct them towards it (with respect, of course). I'm telling you this advice since you added it to the question, which makes little sense to me (in my opinion). I mean, there are a lot of people I've seen here who write really well and end up getting less readers AND followers than the opposite. Good marketing and luck, I suppose. Haha.