-immature, adolescent connotations of words like lol.
-tediousness of using words like lol, due to overuse.
-words like lol rarely describing a person's actual response.
SOTWL, short for "Shitting On The Wall Laughing," bears no childish connotations, provides an exciting, unforeseen response to a comedic situation, and is so obviously not how a person reacted in response to an event, that it effectively eliminates all the flaws of words like lol. (Scenario 1)
In the case where a joke isn't funny, a person may respond with SOTWL anyways, because the use of the expression is funny enough to be a joke itself. (Scenario 2)
Fat Girl: Hey, d'ya want to hang out this weekend?
Guy: Quite frankly, no, I don't.
Fat Girl: Pleeeeeeeeeease!
Outside Observer: SOTWL.
Person 1: Damn, I hate Calculus class!
Person 2: SOTWL.
Person 1: Haha, good one.