Because I don't know anything about you. Even if I was interviewing you and you sat down across the desk from me and we were face to face, I still don't know anything about you. I'm assuming those misdemeanors were mistakes from your past that you learned from? That may very well be true, but anyone can say that and I don't know the truth. Assault, I'm going to assume you tried to injure someone? If I hire you as a driver, you're going to be out in the middle of traffic. You're going to have people cut you off left and right, honk at you, yell at you, etc. I need someone that can remain professional despite the stress and not use the package car to assault other motorists. If I hire you, that would always be in the back of my mind. If I have plenty of other applicants (without misdemeanors) that come off as good as you, I would feel more comfortable hiring them to represent the company. In short, your grievous mistake is a potential liability and you would have to really impress me to make me overlook it.
Having said that, that's just my personal opinion as a driver. I am in no way, shape, or form qualified to hire for the company. So don't take my opinion too seriously. If you do (or have already) applied, best of luck to you.