It's like trying to find something to watch on TV. You end up going through a hundred or more channels to find something to watch because you have so many options. If you only have say 5 options you simply pick one and stick to it. The grass is always greener and you have more fields to pick from than ever.
Settling down with 1 guy is also a massive drop off in attention and praise. If 1 guys blowing smoke up your cunt then that's 1 guy. But what if 50,000 guys were doing it and you could get it any time of night or day just by posting a photo of your knee? How can 1 guy compete with that barrage of attention?