The reason our corners never get a pick is we can never contest a pass in the air, patrick robinson only had like 5 passes defensed all year

From the "Stats don't tell the whole story" category...

Patrick Robinson had 18 official passes defended last season. He was 6th in the NFL in that stat. Combined PD's and INTs, he was in the top 10. He also had a pretty good catch percentage against at 56%.

Conversely, QBs had a 105 QBR against him. His problem is YAC. He was one of the worst CBs in the league in that category last season. With that he gave up 9 TDs. Again, toward the bottom of the league in that category as well.

So he either gambles when he shouldn't or he's not getting help over the top when it's supposed to be there. Or more likely a combination of both.