It's simple really. Humans are motivated by self interest, first and foremost.

Have a personality trait that people like or something that people want and you will have no issues making friends. Don't and people will choose people who have what you don't.

This is especially true for dating or romantic relationships. Love, friendship, charity, or any other of these so called "selfless" things that humans claim to value are little more than self interest in disguise.

All that people care about is themselves so appeal to their self interest and people will shower you with love and affection.