Pretty sure they use the same list as uBlock (and pretty much everything else now, including Disconnect and EFF's privacy badger). My understanding is it's base

Pretty sure they use the same list as uBlock (and pretty much everything else now, including Disconnect and EFF's privacy badger). My understanding is it's based on Disconnect. If you want that kind of flexibility it's easy to add, which means there is no reason for Firefox to have that by default.