I’m pretty sure that a lot of brands won’t let dealers sell a bike online, or even deliver it to the customer still in the box. It’s in the dealer agreement and they’ll lose the brand if they don’t comply.
I think this is it. It's a market controlled by the manufacturers. I wonder if you could start with smaller brands first.
There are some smaller brands out there that sell directly to the customer. Here is an example:
https://moosebicycle.com/?gclid=CjwKCAjwzvX7BRAeEiwAsXExoyjMiIPs_cR8bo8Gn-yEpCsDNtlBz3yYlQjUOiypGfp02HlzBEiJehoCCb4QAvD_BwEMy cousin bought a fixie from them this spring. I picked it up and assembled it for him (came in a box just like every single other bike I've ever built from a mainstream manufacturer).
For a bike that cost him $500, I was very impressed with the quality of it. Granted, they're a smaller company and have a limited selection of bikes. You must either want a city-style commuter, a fixie, or a fat bike. I'm thinking of picking one up myself next year.
The two biggest downsides for the average layman is the size of the box, and the fact that assembly is required. Bike boxes are quite large, and they won't fit in a normal car, even a hatchback. You either need a truck or a large SUV with the seats down in order to pick it up from the shipping depot (where the bike will eventually end up, because they'll always try to deliver it when you're not home - as happened with my cousin), or drive it to somewhere you can get it built. And as far as assembly goes, if you have a little bit of mechanical skill, you can probably figure out how to put the bike together and adequately tuned. But it's my experience that most people don't seem to have those skills, and will therefore have to bring to bike to a professional to get built, if they don't know somebody who can (like my Cousin who knows me).
Also, I will add that building a bike is more than just putting the front wheel in the drop-outs, inserting the stem into the headset, and installing the pedals. Drivetrain and brakes never come perfectly set from the factory, and will always require some degree of tuning, especially multi-speed drivetrains. Wheelsets will always need the spokes re-tensioned after the first test ride (you build a bike, tune it, take it out for a test ride to 'set the spokes', then you bring it back into the shop, take the wheels off, and tweak the spoke tensions again before putting the bike on the showroom floor). The more expensive a bike is, the more important it is for it to be built properly. Granted, the more expensive the bike, the cheaper it will seem to get it built by a pro. $100 to build a $3000 bike is a relatively small amount, but $100 to build a $500 bike is a huge extra charge.
