The LCS is pretty damn huge in all honesty - it's not many other games that have an officially run league in their major territories with weekly matches in live broadcast shows. Bash LoL all you want but Riot have really done a better job of jumping on that opportunity than Blizzard or Valve have. There's really not that much that rivals it right now. Even StarCraft 2's World Championship Series isn't getting the viewership that the LCS is which is something to ponder considering how massive the original StarCraft eSports scene was in Korea which lead to the founding of KeSPA and pretty much put the likes of GomTV on the map.

As for the US classing them as athletes, it certainly solves a lot of permit/visa issues that organizers otherwise have to deal with. Just seems more like using a legal loophole to smooth the hosting of these events more than anything else.