This is not the only reason, but it's one of the two big reasons: penalties (the other being turnovers / fumbles):

This is Zeke's first TD run (fast forward to 1:29:52 if it doesn't start at the right place)... Great run, everything is great, we take the lead over Indiana and reclaim our rightful spot at the top of CFB (lol).  But just look at Wilson trying his damndest to get this play called back for a completely unnecessary block in the back (right near the goal line).  

I was just rewatching the game and thinking that this is so indicative of what this team is.  Completely undisciplined compounded with guys always trying to make a play.  Sure, he was trying spring Elliot and get him in the endzone and gave a hell of an effort, but damn man, it's painful to think that our top players like Dontre don't have situational smarts to not run down and block and a guy in the back in front of a ref, no less, on a long TD run that puts us back up.

If we just do 2 things: clean up dumb penalties and clean up turnovers / fumbles, we are clearly the best team in CFB.  It's not even close.  Of course, blocking needs to get better but it has been and will.  

Anyway, go Brow... shit, Bucks!