Marvin Miller (remember him) said the stupidest thing the owners ever did was allow multi year contracts. He said if he'd have been the owners advisor he would have told them to never offer anything beyond one year deals. It would have resulted in every player being a free agent every year.
Instead we have the system where the owners get young players at below market value and then make bad deals on veteran players that can really hammer teams. I believe a very high percentage of free agent contracts become bad deals in the later years. Especially on deals over three years.