The answer is, it depends. But here's a helpful article I found. You can see if it helps you make the decision.

https://kjgranite.com/when-and-when-not-to-seal-marble-tile-in-a-shower/#:~:text=As%20polished%20marble%20has%20very,and%20the%20sealer%20wont%20work.

We went through this last year with a marble shower, researched quite a bit, and decided not to seal the marble so any water that may find its way under the tile can evaporate through the tile and will not be trapped behind the tile. I know none is SUPPOSED to get back there but just in case...

"I know none is SUPPOSED to get back there but just in case..."

Yes, actually water normally does get back there as neither the tile nor the grout are waterproof (and not designed to be), and sealer has nothing to do with waterproofing.

I recently remodeled with a very knowledgable designer and GC.

My bathroom floor and shower floor are marble tile.

I asked my designer about sealing the tile in terms of appropriate maintenance. She said that the marble tiles had been sealed when they were installed and that they should be resealed periodically depending on how much use they get.

My understanding is that sealing has nothing to do with waterproofing as the floor of my shower is waterproofed but has to do with maintenance of the marble surface.

FWIW if you get marble finishes, it is best to ONLY have cleaning products that are safe around marble because that way you don't have to worry that someone will use the wrong cleaning product and damage the marble. Other than that maintenance of my marble surfaces has not been a problem