I've thought about it a lot and I have to say they worst part about it is the feeling of defectiveness it gives you. Like you're not whole or were born with something scrambled inside.
I mean sure there's the biological desire to fuck something. There's also the envy of missing out on something everyone else is doing and there's also the feeling of rejection knowing that because of your looks, personality, upbringing, or a combination all three; that you've been found wanting.
Another factor that comes into play is how degenerate or sexually "open" society has got. You can watch 13-16 year old boys dry hump their beautiful gf on a tiktok or instagram clip and you can't help but think "what's wrong with me? I'm a failure at life"
But what really gets me, and I imagine a lot of other people here, is the knowledge that you lack the ability to do something that everybody else is able to do. It's not just about being angry that everyone else is fucking, it's knowing that you can't and asking why.
It really wears at your self worth knowing this. It's within the biological imperative of every organism to want sex; alongside food, water, friendship etc, but you can barely manage the latter three. You are literally a failure on a biological level.
This is further compounded by the complete inability of non virgins to empathize. Everyone, whether on this site and even on this board, who says it doesn't matter always turns out to have been someone who lost their virginity whilst a teenager or in their early 20s; like everyone else. Most of them aren't being intentionally obtuse but it gets incredibly frustrating hearing someone try to comfort you over something they literally cannot comprehend.
It just leaves bitterness and suicidal despair knowing that basically every human can achieve with ease what is unreachable to you is absolutely gut wrenching. It's painful knowing you can't experience the most simple intimacy with a woman.