Because online there's a prominent enough and loud enough push back on the "cat lady" trope that that's what they mostly see. Unpartnered women basking in and enjoying happiness. Without them.

They're not seeing the women who are lonely and want a partner too.

The disconnect is in a failure to realize that life with many of them makes women miserable. You have to appreciate the almost comical irony there because if they can't tolerate themselves when alone to not fall into fits of despair and loneliness so extreme they become suicidal/homicidal, one wonders why they assume their company would be such a boon for women.

They must think we're all masochists.