Why does liposuction usually leave the abdomen dark/disfigured?

Hello dear, that depends on the type and also the way performed... Also the patient healing process. But usually, liposuction leaves bruising all over the places where was performed 

Very difficult to respond to your question. There are always risks in having any surgery. Plus if you are not a candidate because of deficiency of areas of fat than aggressive lipo might cause there discoloration issues? 

Lipocontouring does, of course, cause bruising during the immediate post-surgery period but certainly does not "usually leave" the abdomen dark or bruised-looking over the long term.  Bruising in some patients can seem to take a loonnngg time to resolve but usually does with limited sun exposure and time.  I tell my patients that the belly button will look different after lipocontouring going from a rounded, soft-looking umbilicus to a hard-edged one that is more indicative of a better built body.