In my opinion being courteous is one of the best and easiest thing you can do as a martial artist. Being polite and respectful is a cornerstone of being a good martial artist, and it is expected in any good studio. And courtesy is shown by a martial artist who cares for themselves and their art.
"Karate begins and ends with courtesy" and "A karate man is always a gentleman first" Were some of the principals I began to truly understand when I was a young martial artist. It is really easy to wrap your head around the idea that if you are nice to people they'll be nice in return.
As I have grown older I realized it really is true. When you treat people with respect and kindness they treat you differently as well. I like to tell my young students that its like unlocking a cypher to adult communication. When you say Yes ma'am or sir, adults almost have to stop and think about what they just heard. I Western culture it almost shuts people down, because in this me first culture we have cultivated the idea of courtesy has been lost in a way I feel has been detrimental to our flourishing as a society.
That's not to say I am perfect in any way. I forget my manners and courtesy all the time. As easy as it is to practice it is just as easy to forget. Emotions make us dumb sometimes. But the idea of being mindful and forgiving and empathetic isn't just a martial arts thing. religion is big on it via the golden rule. Studies on happiness have shown that when you practice courtesy to others you are happier yourself. I think a lot of that has to do with not feeling the shame of losing your temper, but I am not brainy enough to know for sure.
But really why I like to really hammer courtesy home is that " respect is valuable that it has to be given away". This is my personal reminder that respect has to be earned by demonstrating first. You don't get to just walk around and say "hey respect me!" I mean you can but that is fear and that's a different article.