Arxiv isn’t peer-reviewed and doesn’t count as a publication. If all you want to do is get your work out there, you’re free to do it, but it’s highly unlikely anyone will see it.

As a researcher, your greatest hope is to learn something, tell other people about it, and have them build on it. That’s not going to happen if your paper hasn’t gone through peer review. It’s also not going to count as a publication as far as your career is concerned, and that bit does have to do with your professional standing, which counts from everything from career advancement to, yes, grants.