Those games are much more self contained arena type games - the scale and complexity of the division coupled with the network architecture used doesn't tend to work well for anti-cheat.
At the end of the day the cheat authors are usually 1-2 steps ahead of the anti-cheat software anyhowthe best remedy is well admined servers frequented by a regular group of people who actually have a love for playing the game but again unfortunately not something that fits this game very well.
I get the feeling that the original vision for the game was completely different gameplay wise - probably more QTEs (yuck) and roll the dice old school MMORPG style combat where you merely selected the enemy you wanted to shoot at and everything else was just roll the dice and actual aim or movement, etc. didn't matter.
Otherwise I just can't understand the choices made - for instance not to use TCP in this kind of context is drummed in early on however you learnt network programming.
PVP wise though the smaller stuff needs to embrace the community more in some way or other while facilities active community moderation and so that cheaters stand out and stuff like the DZ really needs to move towards a bigger focus where "clans" can work towards objectives and things like camping bottlenecks, etc. become more an incidental part of the action - reducing the impact of individual cheaters and where they do go all out head snapping, instant killing BS they stand out like a sore thumb with a lot of people knowing about it helping to get rid of them.
Because Massive are too pigheaded to admit that they wrote one of the easiest game architectures to cheat with and do something about it. Or they just don't want to spend the money on a cheat prevention program.
Ironically, if their claims about finding and banning cheats is true, they are probably spending more money on retroactively banning than a proper cheat program would cost.