That's a very pertinent question:

"So people who try to develop relationships but are rejected or avoided are choosing to be alone? "

I've wondered about this myself, since I was unhappily married for 20 years, wanting to be alone, then dating for the past 10 years unsuccessfully, though I gave it my all! NOW, I'm actually quite content in my solitude, pursuing my interests, my Master's degree in Art and finding fulfillment in my own pursuits. Maybe this is "sour grapes," and I've wondered about that as I find more and more satisfaction in my life alone. All I know is that at this point I can't imagine accommodating another presence, especially male, wandering around in my space.
Patty