Winnie-the only scenario which a bochur will behave in that fashion you stated(rejecting freely since there are many options) is only due to the fact that at 21 they are probably not mature enough and don’t feel a need to settle right away. They will want to look at all options. The same goes for girls though. At young ages they feel they can get anyone they want and why settle for some shmoe who just has an average job. It’s rare to find young girls who are “attractive” getting married unless they have found someone perfect to their standards.
It’s a shame that people only mature and know what to look for when they get older and then options are more limited. But that’s how it works. I’d say by age 26 and up is when girls start to be more open minded regarding a potential guy. Even then…