Development and production of hardware is fundamentally different than software. Thinking and making are separated much further in time and resources, and copy-paste simply doesn't work the same way.
The statement of open sourcing hardware and focusing solely on the software implies someone out there is magically going to make high-quality hardware for your software to run on. That's a thorny assumption.
Most IoT is more than just PCB's. There are also enclosures, actuators, and physical UI/UX. Relying on someone else to provide that much of the user-experience is a brittle proposition for a business.
Some products will just not have a big developer community behind it also.
But again, online community is one of the biggest defense as a company and I definitely software should be a focus in most IoT companies.