Because even in bad QB drafts, teams are always desperate to get their QBOF. They had a special on it this morning on the NFL Network. I think it was the '93 QB class they were really bagging on, that didn't have talent at all but still had really high picks.
Let me ask it this way...do you believe there is no such thing as a bad QB class? Because if you do, then go on to show me a draft--any year--where a QB wasn't taken in the 1st round, or even the top 10. Just because teams will take a QB high, or even #1 overall, doesn't mean they're right to do so.