Let me clarify my statement: Most *employees work at companies that don't allow you to ...
Yes, I'm sure most startups are lax, but big corporations are not, and there's way more engineers in total working at big corps than at startups. When I said "companies" I didn't have startups in mind.
I'm genuinely curious how common that is these days. I certainly work on personal computers and a lot of people I know seem to do so as well.