I grew up and my kids grew up writing thank you notes as well. I just wrote one today in fact! And there is nothing wrong with writing them if you wish after a college audition. I don’t think it is necessary to thank someone for an opportunity to audition to admission to a program when you paid for the audition opportunity and it is the regular part of the admission process. It is not the same as, for example, my kids writing thank you notes to any faculty members who went out of their way to meet with them one on one on a visit (lined up in advance) or an alumni who conducted an interview as a volunteer. I’m just saying that there is no down side to writing a thank you for an audition, but I don’t think it is a must and surely many get in who don’t. I don’t think you have to remind the auditors of who you are. I DO think thank you notes are the right thing to do for a one on one interview, or meeting, or when someone goes out of their way for you, or gives you something, etc. The audition for college is part of the process of being admitted. They really are not offering anything to you. You pay to apply and audition. Put your best foot forward on your application and in the audition room. No need to really promote yourself or keep reminding them of yourself unless you have new information to share with an update since you applied or auditioned.