So this is a personal theory of mine and something i have noticed other men do aswell, those i consider Alpha Anyway.

When a women wants to find a boyfriend or a man in general, and not just a casual fuck buddy she always goes for the one she considers highest value (dont want to brag but it often happened that it was me because i dont give a fuck) Anyway so when the guy rejects (did this multiple times) she goes to the second best male which she considers highest value immediately like sometimes seconds apart its fucking crazy, had rejected a girl only for her to strike a conversation with the second guy i would consider alpha in class immediately. Now of course he just ignored her and he didnt give a fuck.

Now as a person i just dont view being sloppy seconds as a good thing because if you are not considered at the top, then she will just leave you the moment she has a chance for someone higher then you on the hierarchy, if you arent her top choice from before, its not really about relative value from other men (as complete losers that exhibit alpha behaviour are considered top by women) but its about having spesific characteristics for a women to legimitately be attracted to you from a mating and bonding perspective.

Now about the evolutionary reason for this, i believe it could be that men that we could consider "alpha" have a biological reason for this, and that is those men that accepted being sloppy seconds just get cuckholded ending up raising another mans children meaning essentially becoming useless. Or wasting resources on a mate that isnt actually going to mate with them and they end up turning into walking welfare centers.

Now i noticed that certain people i know especially a former friend of mine, literally would take a girl i rejected even tough he knew he was just sloppy seconds for her (and no, not for pump and dump bet a legitimate relationship) only to be left the moment she finds a guy she actually likes.