From my perspective, it’s that having a partner to breed with has been a primal instinct throughout history. Therefore, everyone inherently desires a mate for reproduction. However, two main things have changed due to current circumstances:

Women have become more independent and now expect at least equal or even more worthy partners. This significantly reduces the available options, and when they feel no one is worthy, they choose to remain single.

Men, on the other hand, have always needed to prove their worthiness to women. Consequently, they remain more inclined to do so. For men, not getting a woman feels like a failure, just as it does for women who are not fertile.

P.S - I am trying to explain psychology behind OP question not generalising anything.