Bicycles are not toys. They are vehicles that need maintenance. You can do much of that maintenance yourself if you're a nerd, but the vast majority of cyclists are dependent on local bike shops to sustain the cycling community.
The bicycle/parts manufacturers need a large cycling community to sell products to. The large cycling community will have novice and intermediate cyclists that will abandon cycling if their bikes break down. The novice and intermediate cyclist need local bike shops to do maintenance on their bikes at affordable rates. The local bike shops need a revenue stream beyond labor for maintenance to be affordable. Thus, the major bicycle manufacturers need to give a oligopoly status to the local bike shops in order to keep their user base large.
As a life long cyclist, I've seen the industry grow and wane, and throughout it all, I've seen the vast majority of people think bicycles are some type of sports-equipment. Decisions like this are one of only a few business models that I can see sustaining the community. I'm actually surprised and optimistic to see the major manufacturer Trek start building their own brick and mortar shops in certain major cities, though I'd prefer to see this happen through a major cooperative between the various brands. If you care about making cycling a serious, sustainable transit alternative, we need to maintain the entire ecosystem of ridership, which means the race to the bottom on amazon must be stopped.