Style of mens underwear?

My girlfriend and I are 24. We are moving in together. I have been wearing boxer shorts my entire life. She informed me that boxer shorts are childish. She went out and bought me fruit of the loom boxerbriefs. They are great. Wished I switched years ago. Noticed when all my friends either moves in with a girlfriend or gets married they all have switched to boxerbriefs. What is it with girls that they like boxerbriefs so much?