At first I thought I was just imagining it the past few years, then I saw more than one study showing more and more women are staying single. This is proven on a national level.

Next I noticed that a lot of women I see who are single are quite attractive. Lots in their late 20s and early 30s. Typically they all have decent or good jobs and do whatever they like. Obviously many women and people are single for other reasons and certainly some have personality flaws.
But it really seems like many attractive women are choosing to stay single.

My theory is that there are not enough attractive guys to go around. If you go 50 years back in time, women didn't have the same career opportunities as they do now. So reliance on a male figure to provide for them was very necessary. In today's age, that is essentially obsolete which has dramatically changed dating prospects.