In my bubble, you have to be very careful about hiring because it can be very difficult to fire anyone at a large company. Or it just ends up being such a long, awkward, multi-stage process, that even objectively terrible engineers will get transferred elsewhere within a large company rather than get fired, because it's that much easier for the manager who wants to get rid of them.
Some of it might be a cultural affinity for giving people second chances, but I think a lot of it is just the hoops you have to jump through to avoid the possibility of a future wrongful termination lawsuit if you fire somebody. But I've heard that it can be very different elsewhere, in different industries or countries. I bet it has a lot to do with the legal system too, like whether or not there's a framework of worker protection laws in place.