I'm not being paid by anyone to disseminate anything anywhere, especially here. Go make up a better conspiracy theory.
What am I on about? I'll say it again, slowly.
1. Stipulated: Unaltered Linux itself does not have license problems (Red Hat notwithstanding).
2. Sometimes a company develops an application that runs on Linux.
3. That application may be intended for sale as a proprietary, closed-source commercial product.
4. That application may be based on other proprietary code, maybe under a source license.
5. That application may use other FOSS libraries built from source.
6. It is not always clear that no part of those FOSS libraries, and the code they depend on, are licensed under the GPL.
7. For that matter, the same may hold true for the proprietary code being modified.
8. It is the application developer's responsibility to see that their product is GPL-compliant.
9. That means verifying that nothing being built into the product is, directly or indirectly, copylefted under the GPL.
This is not unique to Linux. The same holds true regardless of the platform the product runs on.
I don't know why you're so certain that it is as simple as "Just don't put in any GPL code." Somebody's library may include somebody else's library that may include somebody else's library, and so on. Those inclusions and dependencies may be undocumented. The author of the library may be an expert in what the library does, and not an expert in FOSS licensing. They may have unintentionally copylefted their code, but the end user has to know for certain before including it in their product.
Maybe you can't be arsed to check all that. Maybe nobody will, or even think to, and maybe nobody will notice, and your product will be fat and happy and out of compliance for its entire lifetime. My current and previous employers have both decided it's both unethical and bad business to be that careless, which is why they pay me to ensure their products are compliant. (Once again, I'm speaking only as myself here, and I do not speak for my employer.)
I'm done now. Please enjoy having the last word.