For less lag and framerate problems.
Thats the only real reason I can think of. Better graphics mean less players or worse framerate. Even though I've seen more framerate dips on this already than in the whole of my time with BC2 and KZ2 put together. Probably why MAG has the worst graphics of most modern FPSs
Never under-estimate the power of the playstation? Shouldnt over-estimate it either.
..I guess. Even if Mag does actually have pretty complicated animation, as well as a high amount of different textures.. with the largest view-distances in any fps. It seemed like they were prioritizing a bit differently..
And if you listen to what DICE is saying about updates and so on - what they're talking about is the amount of updates sent across the network. The updates in the game-world can be done quickly once they're received - there are lots of games on either ps3 or xbox that have world-updates done through asynchronous thread support that would allow massive amount of updates like this. And the graphics won't really be more complicated just because you have more world updates. Besides, that can - and without a doubt will - be scaled for the consoles anyway.
But if you're stuck with a requirement on low bandwidth usage, and wish to minimize the impact of lag from unfiltered clients and random matching - then of course reducing the amount of players suddenly is very sensible.
Still sucks, though. That they can't start to filter clients, and require a high downstream.. do something like GT5 for example - make "quality"/updates and bandwidth a choice depending on your connection. And then favour matches based on your connection quality.. Something like that would work just fine.
Would work great for the current system they have in BC2 as well. Which, by the way, will not lag at all if all the clients in the game has a reasonably good connection towards the host. But since they allow the "global servers", it's lagging like crazy. ...I mean, even Halo has a "recommended games" option when matching right now. It's not that it's impossible to do it without simply refusing people to join a game.