The problem is that in the current NFL, your QB is either worth 18 million a year, or like 4 as a backup. Unless the guy is playing on a rookie contract or an old veteran without a rich pedigree (Josh McCown) most people who start are getting paid. There just are not enough good QB's in the world, especially with the college spread being the preferred type of offense currently. If you have a guy who you think can be good (remember, #1 pick, played well in quite a few games early in his career, but ended up being injury prone) who is going to be put in an offense where he can be successful, you have to go for it. Hitting the reset button on QB is too painful.
Look at the numbers of who made what in 2014.