should you ask out every girl in sight

I was waiting outside Clarendon Ballroom, just talking to girls.

Most girls were inside the ballroom and i was just outside on the street, but I had two conversations with two girls that went rather well. One was not particularly attractive but one was like a really good conversation, and in niether case did I ask their phone number. I think if you don't ask them out, you preserve your dignity a little or you seem more secure, if you don't ask them out within 5 minutes of meeting them. But then I'm like, I'll never see them again, what do i have to lose?