skribs
Grandmaster
I also feel like martial arts is alone in this. Essentially the idea behind belts (besides pride and bragging rights), is that every new belt indicates you're more advanced and that you're able to handle more advanced materials. When I played piano, my piano teacher didn't require me to pay for a test to start learning more advanced songs. With bouldering, in places that separate between beginner/intermediate/advanced, you don't have to pay to get evaluated to go on one of the higher levels. The lyra gym near me has different level classes too, and the instructor there from what I understand just informs you when you're ready. It seems unfair to pay for a service/training, and then be limited from more advanced aspects of that training based on your financial concerns when you're already paying for that training.
Tell that to my collection of guitars. Or golf discs. Or guns. Or my gaming PC. Or my lightsaber collection. Or my...well you get the idea. A lot of hobbies you can have get more expensive when you get more advanced.