How much of an 'offer' can they get from a school? Maybe they can be promised to not red shirt, or to play a certain position they want, but I doubt any coaching staff will stick to that if it doesn't work out for the team as a whole.
Another angle might be that you give a team hope (SCar over Clemson or vice-versa) so that they don't recruit your position too heavily. But I wonder how effective that would be if you don't commit. Of course, committing is pretty meaningless these days.