It doesn't even need to be a startup: hearing aids are techically inferior to mid-range earbuds, yet cost more than 10x more. I'm guessing it's a certification+distribution issue, like for smartphones in the US. I've heard Bose has something in test though ?
It’s not quite the same, many people with hearing loss only lose hearing on part of the spectrum, so it’s not just about making things louder, it’s about making the specific frequencies louder in ratio to the loudness of the noise.
It’s not only that, the hearing loss may be very different in each ear. I don’t need a hearing aid for my left ear. If I lie with my left ear on a pillow, I will hear almost nothing. My yappy ankle biter dog a 3ft is audible. This means that if I use an OK headset, shift the balance as far right as possible while keeping the left speaker on, then turn my iPhone all the way up, I hear stereo at a comfortable but not loud level. Surely that amplifies some frequencies way higher than they should be amplified.