It surprises a lot of homeowners, but tile and grout are not waterproof. Grout is porous, and over time water works its way through it. What actually keeps a shower dry is the waterproofing system behind the tile and under the floor.
A properly built shower starts with a pan sloped toward the drain, so water never sits under the tile. The walls get a continuous waterproofing membrane, either a sheet product or a liquid-applied coating, with corners, seams, niches and pipe penetrations sealed. Many installers also flood-test the pan before tile goes in.
When that layer is skipped or done poorly, the damage is slow and hidden. Water soaks into the wall framing and subfloor, mold grows behind the tile, and by the time grout starts cracking or tiles loosen, the repair means tearing the whole shower out.
In Florida's humidity, this is even more important. A bathroom that never fully dries out gives moisture more time to find weak spots.
Every shower we build gets a sloped pan and full waterproofing before a single tile is set. If you're planning a bathroom remodel, ask any contractor exactly what goes behind the tile. It's the most important question you can ask.