I'm also over 50 and single, but I mainly consider this to be due to my own issues, and not because of a lack of men.

Over the years, I have always encountered at least some single, heterosexual men in my age group, both at work and at music and other activities. A number of them have been very nice people, and most likely still single because of being shy or lacking in confidence. Although I may have not found "the one" for myself, I did not see these men as losers.

I also have met plenty of men over 50 who enjoy pursuing various interests and are not just sitting home watching TV.

Since I don't know the OP or other posters here personally, I have no sense of what other people's personal issues are. But it may help for some of us to do a little more self reflection when things don't work out, and look at our own role and attitude in the relationship process. (I do not consider myself either an optimist or "positive thinker", by the way, just a realist.)