1. People do not want hearing aids (typically they do not even want to accept they have a hearing loss). You need to spend an awful lot in communication and marketing and humans you can talk to in a store to convince them to try one.
2. Hearing aids are not glasses that you put on and the problem is solved. It takes 6-12 months to get the full benefits and you need multiple visits to the store with humans to hand-hold you through the process or you will just stop wearing them.
And did I mention the average customer is 70 year old? Explain to me how a 70 year old that does not want a hearing aid will buy one online