Captain Crunch
Veteran
I'm sure he had his chance to sign wherever when he was a FA, they didn't franchise every single year. Football is not like those other sports though, making more money is usually more important than playing for a contender (ala Mario Williams). Not to mention the parity in the league (Fitz went from playing in the SB to playing with a bottom tier team)
If you talking about basketball(as far as superstars and players 31 and older yes), baseball it's about the money. With that said, in football, there's no true FA, so players never really get their market value. It's interesting how NFL is the most profitable league in North America, yet is has the worst union.