collaboration is the killer feature tbh. overleaf is basically google docs meets latex.. you can have multiple coauthors editing simultaneously, leave comments, see revision history, etc.

a lot of academics aren't super technical and don't want to deal with git workflows or syncing local environments. they just want to write their paper.

overleaf lets the whole research team work together without anyone needing to learn version control or debug their local texlive installation.

also nice for quick edits from any machine without setting anything up. the "just install it locally" advice assumes everyone's comfortable with that, but plenty of researchers treat computers as appliances lol.