Most young women--at least in Holden's time--wanted to get married and have babies and homes. If a girl was pretty she didn't have to travel far from home to find a suitable husband. Some were getting older and seeing others get married and having children without having any prospects themselves. The three girls who have traveled to New York all the way from Seattle are still really looking for husbands, whether they know it or not. Holden understands them a little bit, but he doesn't understand that they are types rather than individuals. Holden describes them truthfully: they are not bad looking but not great looking either. In fact, part of Salinger's technique is to present character types as individuals because his viewpoint character and narrator is still so young that he hasn't had enough time to recognize types as such but will see them as individuals. Even intelligent young readers will recognize Salinger's characters as types because they will remind them of people they have actually known in real life. All three girls from Seattle would like to find Mr. Right. They don't have the slightest idea where to find him. He could come out of nowhere. They obviously despise Holden because he couldn't possibly be Mr. Right. He is still just a kid. These three girls are just circulating, knowing that they need exposure in order to have a chance of attracting the kind of man they all want. There is as much competition among women for men as there is among men for women--only women don't make it so obvious. The three girls from Seattle have to travel around together because they don't want to be visiting bars alone or to appear to be too lonely or vulnerable. Much of this Holden, only sixteen years old, does not understand, although his creator J. D. Salinger understood it very well.
Some of the characters in The Catcher in the Rye who are obvious types, in addition to the girls from Seattle, are:
The two cab drivers
On Chapter 10, Holden is at the Lavender Room, a lounge at the hotel. In there, three girls who are from Seattle are visiting NYC and he tries to impress them by ordering drinks, smoking, and acting cool. The girls, however, are not impresssed with him because they want to spot celebrities at the bar. In the end, they leave and he gets stuck with the tab.
He is repulsed by the girls, and contrasts them to Phoebe and Allie, who (in his book) are unreproachable. He goes on in a rant on how these girls are extremely superficial, how the adult world is full of phony people, who only care about what's in the outside. Yet...wasn't he also doing the same thing? Wasn't he also acting superficiallyn in order to fit in?
What this says about Holden is that he is great at whining and criticizing others, but he has a hard time applying his philosophy of life on himself. He has a great deal of double standards, and he is no different than the people he criticized. He has a view of life that is convenient for him because it allows him to make excuses for his lack of gumption and his inability to build social skills. His views also help him hide his feelings and pretend that he is actually strong-willed and corageous. Which, he is anything but.
The scene at the bar with the three girls from Seattle reveals just how judgmental Holden is. It also shows some kind of hidden sexism. The moment Holden met the girls he had already come up with stereotypes with the girls and were calling them names. He had already decided 2/3 of them were ugly and the only ok one aka the blonde one was very dumb, despite only having known them for less than an hour. When he danced with the blonde, he gave up the idea of a conversation and mentioned the fact that "Girls who are dumb can really dance."