Why is dentures a private benefit?

Why is dentures a private service and only partially covered by health insurance? Or rather, why are the actual costs higher than what the insurance company offers?

Having your teeth out can have serious psychological consequences. Even if it's possibly your own fault that you don't take care of your teeth. However, the costs that dentists charge are simply unbearable, and I don't understand why that is. The material certainly isn't expensive. 1-2 silver, amalgam, or plastic crowns cost less than €950. My current bridge costs just as much. The statutory subsidy, or double the subsidy paid by health insurance in hardship cases, is much higher, at around €1,200.

Unfortunately, my bridge isn't as good as I thought it would be. It's painful and uncomfortable, and an implant is much more expensive than this one.

And I don't even know if my insurance will cover it again if I change dentists. Initially, the dentist promised me a white bridge, but it turned out to be silver. I went with it after all. Before that, she had made me a white bridge, but without replacing the middle tooth. I assumed it was just to protect the teeth, as she also said. However, I don't believe that anymore. The plastic became like glass after a while, but I quickly took the bridge off because I wanted to test how tightly it was hanging there. I'm also assuming that this bridge was supposed to be the right one, because it just became like glass, and I really don't know why she just put a protective cap on it after rubbing it off instead of having the real bridge made or inserted right away. Now I have a metal bridge in my mouth, which also hurts, and I have no idea what to do now.