The problem is, for average people basic social decencies is considered bare minimum but for conventionally attractive people it is considered transactional.

And sometimes it's not even a conscious choice.

It's like if you're physically attracted to a guy by let's say 5 points. Their act of kindness will add like 0.5 point to your total attraction to him even if it's very basic. And if you're physically attracted to them by 20 points. Their social decencies can add 2 points to your total attraction. You get the formula. Now let's say you don't find the person physically attractive. Then their acts of basics decencies will be counted bare minimum and the default. Even their high effort acts of kindness will still add no points in their total attraction as a partner.

The problem with nice guys is that they think these basic or even high effort acts of niceness will have the same impcat of an attractive dude.

So their reasoning is right. They just get the wrong conclusion.