In the late teens/early twenties, finding a partner is harder for guys than it is for girls.
If you're a girl who's decently attractive, you can simply wait for guys to approach you, and you'll find a boyfriend quite easily. Many girls in that age range can find a new boyfriend with the snap of a finger, even if they're only average looking.
Being a guy, it's not that simple. If you're a man, you're expected to approach and initiate with girls you're interested in, which means shy or introverted guys usually have a harder time meeting girls. Really attractive men may be able to get away with shyness, but if you're average looking or lower, you can't get away with it. You're also held to a higher social skill standard, and any wrong move can easily put you in the "creep" territory, which is especially true if you're unattractive.
And don't even get me started on online dating. Tinder, Bumble, Hinge, all of these apps only work for the top 10% of guys looks-wise. Online dating is a cut-throat competitive world for straight men, that can easily break your self-esteem if you're the sensitive type.