1. The burden it would put on smaller manufacturers and companies (every little regulation adds up), especially difficult considering the comparative lack of qualified developers
2. Drivers != Quality, Upstreamable Drivers. Making the judgements of Linux maintainers legally binding is a bad idea. Case in point: Apple has Linux drivers internally, they’re just not complete or upstreamable. You would be forced to fight the Linux maintainers (and the power trips they already have!) in order to legally sell your product.
3. If we can force companies to support Linux, why not force all websites to support Firefox? Why not force all desktop programs like Adobe to support Linux? Etc…
4. What about poor FreeBSD? Serenity OS? That guy who still loves OS/2?