If you remove the abstractions down to "someone emits some electromagnetic radiation" then yeah it makes no sense. Just like saying "someone out there is mixing hydrocarbons with rocks and dumping it on the ground that you may or may not care about".

Most people would rather discuss it in terms of "funding an independent source of media" and "building road infrastructure to move goods and services".

I'm not sure comparing radio with roads is correct.

For roads, maybe somewhere it's the same, but there are also funding ways that work differently. If you use the road (have a vehicle) you (probably, depends on where you are) pay the tax, either directly or included with the fuel price. If you don't drive a vehicle but use the roads indirectly (because the services you use, use that roads) you pay indirectly - trough your funding of those services and their respective use of vehicles. E.g. you buy stuff in a grocery store, the store pays to a transportation company, the transportation company pays taxes for their trucks - everyone's paying for what they actually use. So, it still feels fundamentally different from the broadcast taxes to me.

Public schools or libraries are probably a better analogy.

In the US, various forms of taxation at the federal, state and local level go in to providing funds for public schools. Everyone pays for schools even if they have no children. The only significant exception is that in some places, parents can receive vouchers to pay for private schools. Either way, the goal is that everyone receives a basic education to make a better society.

Everywhere in the US I've had a library card, it was similar. Libraries are funded by general taxes and their basic services are provided without charge to users who live in their tax area (county, most places).

Whether publicly-funded radio stations are a valuable public good in this way is reasonable to debate, but that's the model.

Depending on a single revenue source is the exact opposite of being independent; which is why they are always that outraged if someone proposes some reduction in funding. They are 100% dependent on parliament will. (...whether this is something you want your media to be, I don't know. It's a very German thing.)

But of course it's not only financially. The German Rundfunkrat is basically designed to be the very essence of what other cultures might dispraise as corporatism. - Despite it's justification as some cross section of society.

I'm not necessarily against the idea but the institutional design of German state media is arguably very bad.