There are already several pools available, people just seem to prefer 1GH for different reasons. Even if there was a p2pool I'm not sure it would take much away from 1GH.
Perhaps. But it may be more enticing because it would clearly lead to a more decentralized network and if the options there and easy to setup XCN could be the clear winner in this regard since every other network would require full blockchain to do so.
The nice thing about 1GH is that there is no need to setup an account. I too, like this model. There is also the fact that mining on another pool at this point would basically be equivalent to solo mining.
It may not be a problem now that 1GH is running the network but long term viability would require lessening their share. P2pool's benefits would be worth the switch.