People who likes gambling will bet on anything as long as there's some kind of "chance of winning" over others. Just checked the sports betting menu on Rollbit and Badminton isn't a thing there yet, I see tennis, table tennis and squash though, which I think I haven't seen yet or how it's being played.
Honestly badminton is something I do not even remembered until I saw here, and there are people who wager on it. There is a "casino" or betting platform or whatever you want to name it which also has a situation where you literally need to focus on what is going on around the world, it is not sports or anything, it is like what the Brent oil price will be above 100 or lower etc etc.
That kind of place exists, which is a proof to what you said, it is impossible to just have something that is too out of reach for gamblers, if you could attract customers to your website, then they will gamble on whatever you provide, including oil price or badminton, nothing is too niche.