Stone showers we see are typically designed using calcite based stone like travertine or marble. These surfaces are subject to low pH etching and become a substantial part of a refinishing marble project that can be avoided, if the chemicals that can cause these marks are limited in use.
The reason these low pH (or acids) are used is that the stone shower is typically subject to the same build up of soap film that any shower would be. The difference being the porous nature of the stone surface allows the soap film to penetrate and become difficult to remove. A chemical that mimics an acid capability (since soaps are predominately alkaline based) is necessary.
The other problem we see with stone showers is with the install itself. Often the edges and corners of the shower are filled with grout. Grout is a mortar, and works fine between the tiles, but in corners and edges grout will shrink and holes will form. If left unattended, water will seep into these holes and can in time become a source of water damage. The grout in corners and edges needs to be replaced with non-sanded caulk. The caulk contains a latex that will contract and expand, reducing the chance of holes forming.
The best way to keep a polished stone shower looking great and to avoid almost all problems requires a lot of work, but is well worth it. The shower should be squeegeed and wiped down with a towel after each use. A small fan should be place near the door and run until the shower is dry. I have seen showers handled in this manner that are several years old that look like they were installed yesterday.