I dont know why, because I really like NV but for some reason I just lost interest after awhile. I really liked the factions and HC mode but I dunno. Just got bored. It could just be because I played FO3 for so long.
Seems like Skyrim favors longer quest lines over more faction which personally Im cool with.
Heres the thing though, this isnt FO its TES. If they tied to many quests up with factions, people would be on this forum FREAKING OUT that they couldnt do any quests without having to join some faction that they dont wanna have to join.
I lost interest in it New Vegas because I got to a point where I was discovering location after location with nothing and no-one there to interact with except maybe a swarm of cazadors or a radscorpion. Then there was also the matter of all those game killing bugs.
I agree that the factions were more interesting though - but it was also horribly easy to write-off or circumvent quests without meaning to. The Mr House/Legion quests were seriously flawed.