Home is in no way attached to gaming on the PS3, whereas the Gamertag on the Xbox 360 is. That's what you're saying, right? That completely hits the nail on the head. If you play games on the Xbox 360 you get achievements and scores in multiplayer that directly make your Gamertag 'more valuable'. If you see someone with a big list of played games and a lot of achievements and gamerpoints you'll see them as real gamers that know what they're doing. It grows your e-cock, in a matter of speaking.
The PS3 misses this. They finally have trophies, but Home is in no way related to them. If it was, the PS3 might hit it big. How many people like micro-transactions? There was a rumor Diablo 3 would have micro-transactions, and I can't remember anyone jumping up and down in excitement. Who likes dishing out cash for every little thing? Let's say you have to pay a tiny amount of money for everything you buy on WoW. Even if it would be cheaper than the (bi)monthly fee you pay now, it wouldn't be half as popular as it is right now. That's what I think..