There is a lot more to your average EE CAD package than just wiring up some parts. That's the easy bit. Rules checks, physics, placement, packages, PCB design, (auto)routing, Gerber files and all the other 'goodies' are required before you can take on the big guys.
Schematics is an important element in the whole chain of developing hardware, but it really needs a lot more than that.
That's a large number of man-years, and by going the software-as-a-service route they gain some advantages but are also stuck with a number of disadvantages, the largest of which is that they won't be seeing the benefits of user contributions at a level where it will move the needle. Of course there will be contributions to the parts library that can be shared, which is a step.
The 'perfect tool for open-source hardware' would benefit from being open-source itself.