Scarring beneath the skin and within the tissues makes pulling the skin during a leg lift and some other surgeries harder. Wrinkles and irregular skin texture are easy to correct when the skin is loose from weight loss but harder when lipo has already been done. Also, a thin layer of fat actually helps make the skin look a little smoother better than if it's too deflated and all fat has been taken away by lipo.
Large, isolated fat deposits are good candidates for lipo.
Lipo is also good for defatting the legs or arms if they are still big prior to a lift in a patinet at or near goal weight. , BUT I do the lipo in skin that is generally going to be removed so the sacrring is not such an issue.
My caution is to avoid practitioners who may offer you lipo when a lift is what is actually needed, or to perform lipo as some kind of substitute for further weight loss.
Hope this helps.