PFT: Dungy out as Colts coach

The interviews aren't about getting that specific job.

Being able to interview for a better job improves your own stock amongst your peers and gives you leverage against your current employeer. It also allows you to impress powerful people who otherwise would have no other exposure to you.

If i'm black and Jerry Jones wants to interview me, I don't care if he's basically hired Garrett, I go and interview. If I impress Jerry enough, even if he doesn't hire me, I
1) I get the prestige of having attracted the interest of an owner like Jerry Jones
2) I establish myself as a "wanted" person, which may improve my position with my current team
3) And I establish a positive word-of-mouth reputation as Jerry Jones relays my good impression to other owners

This is really true of most any workplace, but it's especially true in the NFL because the NFL is an ultra-exclusive club where word-of-mouth recommendations carry an inordinate amount of weight.

"It's who you know" so why not have the opportunity to get to know and impress more people?