cHode, you keep in mind that MTA is not a game it's more like a client that enables you to play online with GTA 3/VC. Quake 3, BF1942, HL and so on have online capabilities built-in and the developers has probably done everything in their way to prevent cheating online, but the difference is that they were able to code it directly into the game.
MTA is a client that uses the GTA VC engine and everything that goes with it and since GTA VC wasn't made to play online with it probably have dozens of exploits that can be used by those who make trainers/cheats.
Maybe this sounds stupid, I dont know, but at least I think it makes sence
And I don't think that 75% of those who play cheats, more like 30-40%. I rarely bump into cheaters but when I do I just change server or play with some people that I trust.