Because what team exactly has loaded up on overpriced FA's and won a superbowl lately?
Its not the way you win a superbowl. You win a superbowl by building through the draft and then, if your a piece or two away fill a few needs. We are nowhere near a piece or two away, so what we'd end up doing is spending serious cash on FA's, while not having built our base yet and we'll fall short. Then after 2-3 drafts have passed those FA's will be gone because of cap concerns but we'll finally have our base. We aren't in the position yet to grab Briggs and Samuel because we don't have the pieces around them to make them successful.
The Redskins and 49ers are very good examples and proof that going after bigname FA's without having a strong team already built through the draft is not a recipe for the superbowl.
The past three superbowl champs? Their entire teams almost exclusively built through the draft. The Colts entire team was drafted.
What should we do with this cap space? Sign one fair priced FA, of which I think Thomas would be, and use the rest to resign key players like Smith, Colston, Faine, etc. You can frontload their deals so we have plenty of cap space when we are finally in the position to plug a few holes with an overpriced FA or two.