Where does google prevent that? I tried on the web login page and I can paste without problem. I'm not sure why they'd prevent you from pasting your login in the first place.
In general there's always a simple way to bypass these websites limitations, like those who try to disable the right click.
Maybe it's a "security feature" of some AV software or IE/edge. Wouldn't surprise me.
I use Firefox on Linux.
I didn't mean to insult you :)
Since you talked about your "(work) username" I thought your employer chose your OS/browser for this particular case.
I didn't take it as an insult :)
While my employer does not chose my OS/browser I am in the lucky situation that most of us use Linux with their favorite distro.
Thanks for this clarification. (Even pasting becomes increasingly impossible. For e.g. Google does not allow me anymore to paste my username at login, and my (work) username is very long... I suppose pasting might offer an easier way scripted attacks. But yeah, most applications still allow it.)