I've worn hearing aids my entire life and manufacturers seeming to focus on miniaturization at the expense of capability always frustrates me. This isn't just driven by business interests though, DSP and EE at that scale are really hard and it's honestly remarkable what modern digital hearing aids can do with such limited resources. It does make me wonder though what would be possible if they just threw a lot of processing power at the problem, like say a Raspberry-pi sized processing unit concealed on the body connected to wireless mics/speakers. This would allow open the possibility to having more than two mics which could help with sound localization, which is something hearing aids are still not very good at.

Maybe it's because BTEs are the only option for someone with my degree of hearing loss, but if given the choice I'd gladly choose (or at least try) a more powerful/sophisticated hearing aid over a more aesthetically pleasing one, all other factors being equal.