As stinger says, why would they care about locking up SC?
I think you have to factor brand preservation into this as well. Part of the SEC's brand is sellouts and strong, passionate fanbases. Unfortunately we don't fit that mold. SEC had #s 4 (Bama), 6 (UT), 7 (uga), 8 (LSU), 9 (Fla), 10 (Auburn), 17 (USCe), 22 (Arkansas), 25 (Kentucky), 35 (Miss), and 37 (MSU) in terms of total attendance (not counting Vandy). Those respective capacities (and don't ask me how they get over 100%, I don't know) are 110%, 97%, 100%, 100%, 102%, 98%, 96%, 96%, 98%, 92%, 100%.
Look at their "candidates" compared to us
A&M - #13 attendance, 99%
Climpson - #18 attendance, 94%
FSU - #20 attendance, 87%
Mizzou - #26 attendance, 90%
GT - #50 attendance, 84%
That's the difference. We may have a relatively recognizable brand across the country, but those other teams do too. More importantly, they have fanbases who turn out in droves both at home and away and drive the gameday atmosphere the sec is all about. I hate to say it, but we don't have that same passion in our fanbase. We have a smaller stadium than all of those other schools, yet we don't have a higher capacity than FSU or Mizzou.
In terms of TV money I'd say we are prob about even with Clemson. Yeah, we are in a much much bigger TV market, but the SEC already has a pretty big share of that market and adding us probably won't do much to change that. Not that adding Clemson would do much either, so its kindof a wash there.