I can't quite fathom why Microsoft would've made this decision, but apparently they will not be selling any 'Mature' or 'Pegi 18+' games through the Windows digital store. Windows 8 will still run these games--it's not like Microsoft is disallowing the execution of these games. Rather, they're opting out of selling them through their digital store.
Does anyone have any idea why they would make such a decision? It seems like they're simply shooting themselves in the foot. After all, a large number of game sales are of games that fall within the 'M' or 'Pegi 18+' rating.
Let me know if you can think of any reasons why them might possibly make such a decision.
Source: Rock, Paper, Shotgun