It's hard to believe that DICE could be so out of touch with the CQC DLC and their rationalisation of it. Yes, I'm sure Metro is the most popular map by simple statistics but there are three reasons for that:
1. Boosting.
2. Unlocks.
3. Familiarity for COD players/casuals.
I think a lot of more casual players play Metro because that's the most accessible map. If you're a casual on Op Firestorm, e.g., and you run from base to halfway across the map only to get sniped or killed by a heli then that's frustrating, so Metro makes sense for those people. But the core BF3 player base want more than Metro. Every half-decent BF3 player I know knows that Metro is just an absolute clusterfudge of a map and that it just doesn't work with 32 players or more. It's chaos with hardly any strategic elements.
And the thing is, it's ultimately the hardcore players who will sustain a franchise over the long run because they're the ones who stick with it for more than a few weeks/months and who are still interested in DLC and sequels years later. So catering to the casual noobs is counter-productive.