Another girl on that app didn't even want to chat with me because of my age. Why don't girls like guys my age?

Again on the app meetme which is for dating, friendship and chatting, I messaged a girl today who is 24 and I am 21. But suddenly she said she won't chat with me because I am younger than her. I told her that I am only 3 years younger than her, but she said me "but its a big difference for me. You are still a baby." I replied to her this "I am not 15 or 16. I am an adult now." Then she said "Yeah but you are in the same range as them, tell me how you are different from them?" Then I said "I am an adult and they aren't and also I am in last year of college and they are in high school." Then she replied "still you are a student so you are young for me." Then I tried to change the topic by replying "haha ok. You are really cute btw." And then she blocked me.