Commuters who want to spend less than $200 on just something to get them moving, parents riding with their kids are also here.
Cyclists who spent 10-20-40 hours per week on a bike. For a hobby that you spend 60hr/mo on it's reasonable to spend $1300 on an entry level road bike and much more as you progress. Especially because it's good for your health.
Obviously there's money to be made with cyclists, but commuters would be so cheap and budget concerned that there's no money to be made from it.
Amazon is perfect because you're not looking for quality. I use a rockbros sweat catcher for my indoor training bike setup and it's great because it's just fabric.
You want LBS to stock $20 pedals? Who is going to buy them? What would the margins on that be? I wouldn't trust $20 clipless pedals (because if they fail you will get hurt/injured) and if they're flat pedals then bmx people would buy flat, but they're going to be so heavy that it'll be bad performance wise. There's only broke students who would buy it, and at that point just get it from Amazon.