They need two different kinds of bug-finders, in fact. They need someone who wants to crash the software and does everything possible to make it misbehave. They'll actually expect a mail program to go out and get the mail, no matter what. But life is like that. You forgive things you know you can't fix.
Programmers are no different.
They just turn off their sensitivity to what's really wrong with their software. So folks like you and me, the stumblers and bumblers, are ideal bug finders. We don't care. We just stick one foot in front of the other. That sounds romantic.