Personally I have no problems wearing collar and tie as I was very much used to it in my previous job. I think it puts you in the right frame of mind and dressing smart makes you feel good and also says to other people that you care about your appearance which says a lot about a person.
Secondly, you are a professional and selling a service to your student, if my instructor turned up for work looking like he just got out of bed I would question the quality of the product and the quality of the delivery! This would no be fare as the instructor has spent a great deal of time and money to get to the position of flight instructor but it's the way we all think.
Thirdly most of us are looking for an airline job and we will all have to wear a uniform then. The flying instructor is as much in the public eye, perhaps more so and it is just as important to present yourself well.
So yes folks I think it is a must, look good, feel good and you'll do good
