> If you buy a home and want it to have a gas stove, why is it the state government's place to say that you can't do so, for your own health?
This is the wrong question to be made. You should ask what should be the safety standards you need to adhere to ensure health risks are mitigated.
The reason why this sort of thing must at all times be regulated, without any exception, is that the personal interest of a corporation investing in real estate by selling it off right away are not aligned with the interests of those who actually have to be exposed to the health risks created by said corporation.
To put it more broadly, just because you are ok with your home causing health problems to its occupants, that doesn't grant you the right to subject everyone around you to them, or even whoever will live in that house after you live.
To make it clear, let's consider doors. You might feel you have no use for a wide corridor and you're ok with custom narrow, submarine like doorways. Except that a wheelchair or a stretcher can't go through. Therefore thanks to your shortsighted and ignorant "why should the government tell me how to be safe" point of view, you needlessly screw over your future self and/or everyone that may possibly live there.
Regulation is not a conspiracy. Regulation reflects hard lessons learned with pain and suffering, and ensures that easily avoidable problems can be avoided easily. We learned lessons from fires and mobility constraints, and thus we have regulation ensuring each and every utility in your home is safe. Instead of having to reinvent the wheel each time anyone needs to build something, we only need to check what's the regulation and what are the constraints.
Air quality is starting to be noticed as a major health problem, specially with higher occupation densities, and thus we have safety lessons that need to be learned to avoid these issues. And no clueless naive spur of the moment bootstrappy individual has a clue about them. Hence the need to impose regulation, because these arrogant morons think they know best when they know nothing. I mean, does it make sense to risk our health just because an amateur didn't even wanted to bother doing his homework?