It could be the kind of people you tend to be friends with, too. It bums me out also when friends seem uninterested in my life and don't even bother to ask about 'big' events. I finally noticed that many of my friends did not seem to have time for me unless we were talking about them... which led to the realization that I have been surrounding myself with narcissists for years.

You're right that it isn't always intentional and more irons in the fire helps