It doesn't have to be profitable for them. It can just exist, be the only option, and prevent others from making a competitive or superior product, forcing others out of the business.
It would be a shame if someone with a physical disability needed to find a different accessible controller for each platform they play on because each one only supports first-party controllers though.
I don't have a disability serious enough to need adaptive controllers like this, but I do have RSI, and when I find peripherals that I can use with minimal pain I stick to them. I have to imagine many with more serious disabilities would feel similarly.