First reason is program name. If you google "GTA SA multiplayer", it will show SA-MP in the first place because it's "San Andreas Multiplayer". Another reason is release date. SA-MP was released earlier than MTA SA DM (don't know what about MTA SA Race, but it has less freedom). Then most players got used to it and now they're afraid of moving. By the way, SA-MP being released earlier means less work and more bugs/less features When I look at feature suggestions topic in SA-MP forums, I see that almost anything players request is possible in MTA.