It may be an advertising gimmick, but it's a gimmick to get more people to the matches, which DOES make a difference.
And to the people who think football should be weighted more heavily, here's the thing. No one is trying to argue that football isn't the more visible sport, gets higher attendance, more money, etc. But that's not what the LSS is trying to measure. The LSS is trying to measure which school, overall, has a more successful athletics program, and more specifically, which school's athletics program is more successful than the other ON THE FIELD. A win in football still only counts as 1 win. Wins in some sports count as Big 12 championships (golf, track, swimming), so you could argue that they're worth more! When was the last time an A&M t.u. football game counted for a Big 12 championship?
Fact of the matter is, no matter what you guys think, if a football program finishes in the top 10 every year, and every other sport finishes 8th-12th in the Big 12 every year, the AD will be gone. The football coach will stick around, and the football program will continue to thrive, but the AD will be toast. So yes, the LSS does matter.