i have a theory on why tracer always has her pants in her ass crack,

i believe the military devolved technology that allows your pants to suck onto a surface causing tracer to have permanent weggies.

i can hear yourself asking, “But why would this be wanted by anyone?” 

well here is why, whenever you have a weggie you need to be constantly running  so you can find an area where you can pick it, this is also where tracers time warping powers come from, if she is caught picking her weggies she must reverse time before anyone saw it. 

^^^^ the mystery has been solved