Our last home, in the southern US, was build in 1980 and two of the 3 bathrooms (all full which is odd) were original and about 35 years old. While the appearance was dated, structurally and mechanically they were sound with no mold, water damage, or other issues. A steam clean of the tile and porcelain, along with a re-caulk and re-grout would have been sufficient to keep them going for quite some time. Our house before that was from 1965 with both bathrooms being original. The metal plumbing had started to fail and there was some rot to the sub-flooring around a toilet but otherwise fully functional and clean. In both cases the bathrooms were like most homes in the US with ceramic tile floors, steel tubs, and tiled shower stalls.
When I think about all the bathrooms I've used while in Europe, most were much newer and all felt like they needed to be redone. The finishes were unlike what's typically done in American bathrooms, some where plastic or vinyl covered while others used wood. They were all small and poorly ventilated, and they all had issues with mold and rot. I'm thinking poor ventilation and choosing materials for style over longevity might be why you feel the need to redo your bathrooms so frequently.