Two questions: Why do some surgeons use a drain for a BBL and some don't? Also, are massages after a BBL needed?

The use or not of drains in a surgery varies from doctor to doctor, technique used and how the patients body reacts during the surgery. A drain can help decrease liquid accumulation after a procedure, called seroma, and a seroma itself can increase infection risk, but a drain itself can also increase infection risk on its own since is an open way of an infection to get in and reach the treated area, so as any plastic surgery procedure the use or not of a drain is not good or bad, the use or not of a drain varies from patient to patient and from doctor to doctor. Same happens with massages, they certainly help with the lymphatic drainage of the area decreasing seroma formation that can increase infection risk and also massages promote skin to re adhere properly after the procedure and also help in decreasing a bad healing process but some doctors prefer to leave the treated area alone to heal by itself. I personally  do not use drains in my patients after a BBL and / or a liposuction procedure but do like massages in my patients after a BBL but only in the liposuction area, where the fat is taken out and not in the injection site, buttocks, where the fat is injected in.

Some use them because they feel it may minimize the risk of seromas( fluid collections). Seromas may be associated with the type of liposuction performed. I do not usually use liposuction devices that are more prone to seromas, so therefore, I do not routinely use drains with bbls.