That is only the "High Profile" cycle because games are not living up to the hype. If the game was in a state where people would want to play it and keep playing it, they would.
People stop playing not because of the Free month is over, but because they don't want to play the game. If game companies would stop rehashing the same product over and over again and come up with someone new and revolutionary rather than evolutionary, perhaps we'd get another MMO that had some staying power.
As it was, SWTOR was just another rehashed WOW clone, much life RIFT and others. Gamers can only play WoW for so long before they start to look at something different. They get sucked into the hype that perhaps whatever new game comes out is "totally different" only to find that it's basically the same game in a new world.
People are still playing it, quite a lot of them really. By all accounts there's still well over a million active accounts which puts SWTOR in the position of "Second most popular subscription based game". Expecting any online game to keep all it's players from launch is simply unrealistic.
Hardly any game can live up to 'the hype' anymore in media system where yellow journalism is making such a comeback. Every major MMO is touted as "the WoW-killer" and "the next big thing" with "revolutionary ideas" and a "brand new perspective" and this and that and the other thing. Regardless of whether any of it is true or not, that's what gets printed because it grabs attention. SWTOR delivered on what it promised, a solid MMO with an unprecedented presence of story backing up many of the traditional MMO mechanics.
Some people wanted SWGv2 out of SWTOR, some people wanted WoW with light sabers, some people wanted DAOC in space, some people wanted KOTOR3, some people wanted it to be like EVE, some people wanted something completely and utterly new.
But that's precisely why these kind of dropoffs happen. You have all these people interested in the game, who give it a try, and inevitably it's not going to be what they all want. It's simply impossible.
So you have this influx of people; some people leave because they didn't get SWG crafting, because they didn't get WoW timesinks, because they didn't get DAOC PVP, because they didn't get a KOTOR story, because they didn't get EVE structure, or because it is designed to feel 'familiar' right off the bat. Some leave because they hit 50 and to them they've beaten the game, some leave because they simply don't want to pay for two subscriptions at once, some leave because they don't want a subscription at all and the free month is enough for them, some leave because the new content didn't come fast enough for them, some leave for Tera or GW2 or D3. Some people just like Star Wars and find out they're not interested in the whole MMO scene.
All of this adds up, affects every game in it's own way, and frankly has little to do with the actual quality of the game itself.