I actually pay more, so I can stream on more devices at once in 4k. It has entertainment value. I have no problem $15 a month for something that helps me relax after work or calms my child when she's upset that her mother and I are doing housework and I wouldn't have a problem paying that once a year as a lump sum. The Prime Video catalog provides none of those benefits as there's just not that much good content. Even the children's programming is mostly knock-off versions of popular shows/characters. The price isn't the problem, it's the value proposition.

The true value of Amazon Prime is shipping and as others have mentioned, the near instant-gratification aspect of same/next day delivery has been bad for our spending habits. Waiting a day or two extra isn't a bad thing and plenty of vendors offer expedited and/or free shipping without a yearly membership.