@Kayriel
Well, think about it this way. If a person was someone who is antisocial, a neet, never had a girlfriend, etc... what would be more relatable? Girls throwing themselves on your dick or girls being tsundere (without realizing they are
romanticly interested in you half, so physically abusive after something you assume you did or accidently caused, but seemingly care a bit about you as a friend) and/or not interested but just friends? The second option is. It is more realistic. Therefore easier to emphasize with.
Also, i feel a common struggle these kind of people seem to have to deal with is that they have contradictory desiers. They want a girlfriend, become more social and socially accepted, but are also incredibly nervous about it. They fear changing the current normal for them is either impossible, undiserved, or not worth the risk. Many enjoy their current lifestyle to an extent, not 100% happy, but it is liveable with a few brief moments to keep it mildly ok. They fear changing would ruin what is already liveable (if the attempted change failed) making it not comfortable anymore. Then what could they do?
So being interested in those who dont obviously seem interested is safer. Those who already are showing interest, I believe to them, seem more like a threat. They are a decision which is incredibly difficult to make on the spot. It is a massive change to their lifestyle all at once. Where the alternative at least is slowly done over a few months to sometimes even years. I bet that slow shift is more appealing.
To people with normal, social lives, this likely seems ridiculous. The options are easily displayed and the change isnt that much of an issue, almost as easy as blinking even. But that is because they are not in their situation. It takes either personal experience or a lot of effort trying to emphasize with them and see life from their perspective to understand.
Ironically, these people are often some of the nicest people too. But a few people easily take advantage of them because of it, or everyone is indifferent to them. Honestly the second one is worse since no one directly hates/dislikes them, but neither are they included in anything unless you are forced to by circumstance or make the effort to be (they must ask to join every time too because no one seems to ever remember to include them).
So girls showing obvious interest in them can often be misunderstood as trying to use them or pitying them and not genuinely want to be friends (or more) with them. They are not use to it, so it does not make sense to them. This also is why slave harems are so popular. A slave cant betray the master (The Shield Hero manga/novel/anime is a perfect example of this and actually discusses it a bit in the story).
