It's very difficult for new component manufacturers to start up, for the simple reason that most people do not build their bikes from parts, so they need to come with new bikes which means convincing an existing bike company to use the parts.

One other issue is that the bike industry is very insular and protectionist. Many bikes and bike components are only available through distributors such as QBP, who only sell to bike dealers.

You can certainly buy good quality components that aren't Shimano/SRAM/Campy, for example the Sensah groupsets on AliExpress have a good reputation for quality and they're a fantastic deal for a high end groupset. But building a bike from parts is a lot of work, only hardcore cyclists do it.