Dorky or not its all in the appearance to the future employer!
Well, to start I would agree with your mother. I own my own business and what she said is right. When you go to a job interview you want to look your best, because your future employer will want to see how you would represent them.
For example. if you were cloned, and you dressed one of you in your normal everyday school attire and dressed the other one to look like a professional and they went to the same interview, asked the same questions, gave the same answers and so forth.
I would hire the professional looking person over you. Just because it is my business and my employees sell my business. They meet with my clients and that is the make or brake time. Clients will judge my business based on how you are dressed. if you are dressed in you everyday school clothing the client will think I have a sloppy business and cant afford to hire decent and well dressed workers. Where as if you are in a suite and tie, the client will be impressed and willing to do business with us seeing how professional we dress will speak louder than words.
Feel free to talk to me about this topic, hope you understand what I am saying.
Its the OX