Journeyman QBs are always playing for their next contract. Remember how Rob Johnson would take terrible sacks because he refused to throw the ball away. It's because he understood that incompletions hurt his negotiating position more than sacks. Tyrod had a similar understanding about interceptions so he refused to take risks throwing the ball. As such, his numbers look good so he keeps getting contracts. Here are his Buffalo Stats (his only extended stint as a starter):
43 Starts/8857 Yards/51 TDs/16 INTs/62.6%
If you are a QB starved team, that looks pretty good. But he was sacked 124 times. Again, low INTs and high(ish) completion percentages gets marginal QBs contracts.