No such reason is causing us not to try impeaching him right now. There are practical reasons aka common sense ones for not attempting it literally, at this point. There’s quite a common sense, practical list that to me is obvious, so no, I do not think the GOP House hasn’t tried to go the impeachment route YET because of the reason you state. As far as Democrats go, nothing would surprise me as to why THEY would double down on support for Biden NO MATTER WHAT, under an attempted impeachment scenario.
Look at what the GOP is doing. Literally, investigating. An Inquiry and a serious one, is going on. Follow it and see what Jim Jordan and James Comer et al are bringing forth and will continue.
Resist the temptation to OVERSIMPLIFY because we know Biden
is the worst ever and should be impeached and removed from office NOW. Cannot happen as you wish nor when you wish.
The problems is that about half the Republican party is perfectly fine with illegal immigration because that what its business interests want.