I think a lot of releases are actually done out of respect. Bringing someone like Woodson or Clay Matthews or Jordy back on a cheap contract would be a challenge to their pride, and not sure how it would look to others around the league.
Driver wanted to retire a Packer and was being phased out of the offense by the time he had that last year. Cobb has lingered for a miraculously long time for a slot WR and wasn't near as durable.


Speaking very generally - unless it's a franchise QB, I'm not sure you should sign a player to a 3rd contract (unless the 2nd and 3rd are short contracts/extensions). By then most are 30 and on the downside of their careers and not likely to produce compared to the contract.