I believe its all coming down to the question "Is there really a market for mature games TRULY aimed at 25+ ages?"
Personally I can't say I've played a game that I would consider mature, partially mature yes but full mature no. Most of them are primarily aimed at the 12-18 year old target group and you can't blame the marketing department for that. I don't know if the game studios are ready to invest in a story that focuses mainly to the after college/university crowd. Those of us that are over 25+ have little free time to spare; kids, family, jobs take most of our precious time. The studios consider that this crowd doesn't have the time or doesn't want to play games because it’s a matured target group and games are for kiddos
Things are just like that so far. Every one I believe would like to see a more mature game but do the studios really want to explore this opportunity?