https://www.liveabout.com/bikes-an-illustrated-history-36577...

For one thing, iron is pretty much a minimum requirement for bikes. Iron was really expensive right up till the point where we learned out to use coal forges. That meant that early bikes were going to be made out of wood. That's pretty much a non-starter. You can't have wooden peddles.

But then, if you want to talk about really modern bikes, you need chains. Chains aren't simple to manufacture, particularly by hand. You need uniformity and consistency. For that, you need manufacturing machines.

And let's not forget the tires. Wooden tires simply don't work well or last for too terribly long (no good having tires that rot. Not to mention how incredibly rough that ride must have been). Rubber is a relatively late invention that was needed to make inflatable tires.