Because these posts lump all men without relationships together. Does the Tumblr user above make any mention of exceptions? Nope. The post boils down to men who didn't date didn't succeed because "skill issue". This would imply that regardless of any other possible causes, I am deserving of ridicule because I don't live life like you.
You yourself make assumptions about me. I was right to say "because of social anxiety, btw, not that you'd care", because immediately here's a reply that implies my social anxiety is not real, or it is but it's not relevant. You assume the worst of me because I dare not have a girlfriend. This is precisely the issue. I've long since moved on from pursuing dating. I don't care if I never have a girlfriend anymore. However, what I do care is if people assume I'm a horrible piece of shit because of it.
Long story short, your comment is case in point: It does not matter what I say. My reply to you is useless. I never had a girlfriend and therefore anything I say is discarded because I have to be an asshole in order for that to be the case.