Why shouldn't I ask a girl to be my girlfriend?
Yes, it must be amazing to have a gf! But again it varies person to person, all my friends who have gf are not always happy! Some time they are frustrated and talks like the guy in "Pyar Ka Punchnama" movie. But when I see their life, I feel jealous!
Coming back to your question, yes, you should have a gf! But again getting the right one is a quite tough, and I am sure you won't propose the random girl over the street. So if you can find a girl, that's awesome! Just go for it.
But being upset for not having a gf is not a good thing! Life is not just to have a girl friend/boy friend!