Grout looks like it should wipe clean, but it's a porous cement. Every mop pass pushes dirty water into it, the water evaporates, and the dirt stays. Multiply that by a few years of mopping a tiled Florida kitchen and lanai, and the grout lines go from white or tan to gray or black.
Home remedies like baking soda, vinegar, and a toothbrush work on a small spot but not on a whole floor, and acidic cleaners can etch natural stone and weaken grout. Professional tile and grout cleaning uses an alkaline pre-spray to loosen embedded soil, high-pressure hot-water scrubbing to lift it out of the pores, and a vacuum recovery so the dirty water leaves the house instead of drying back into the lines.
Once grout is clean, sealing is worth considering. A penetrating sealer fills the pores so spills and mop water sit on top instead of soaking in, which keeps the floor looking freshly cleaned much longer. Kitchens, entryways, and lanais benefit most.
If your tile looks fine but the grout looks dirty, the floor isn't dirty, the grout is. A professional clean is far cheaper than regrouting or retiling, and it usually takes a single visit. We do it for homes and businesses across Lee and Collier counties, any day of the week.