Tile and grout floors can be more difficult to clean than other hard floors because tile and grout is often unlevel compared to other floors. Since each tile is installed by hand and set in grout, the surface of tiles can be uneven. This presents difficulty when cleaning because a vacuum brush roll may ONLY contact tile that was installed slightly higher than others. This uneven surface is further exaggerated when you consider that every grout joint dips further than the tile surface. The difference from the tallest tile to the lower grout joint can be dramatic and not many cleaning tools can effectively scrub both surfaces.
The other thing to remember about cleaning tile and grout is that they are two very different materials. Tile is often stone, porcelain, ceramic, or granite while grout is a mixture of water, cement, and sand. Tile is a solid surface and is great for repealing water. In contrast, grout joints are porous so it will absorb any liquid that is spilled on it. For this reason, grout joints are typically sealed with a water-based sealant that prevents absorption. This difference is important because one is much easier to clean than the other.