I've talked occasionally about the desirability of including periodic hard-floor maintenance in one's janitorial package - that neglecting to burnish, and to occasionally scrub and topcoat (refinish) vinyl tile, and also to machine scrub stone and ceramic, will lead to a poorer looking facility, extra expense to restore the floor, and eventually damage to the floor. Ira_burnish

I've not stressed the health and safety aspects of such ongoing maintenance.

VCT - vinyl composite tile - is porous.  The irregularities provide places for the germs to hide.  A decent commercial finish ("floor wax"), burnished (ultra high-speed buffed) regularly to maintain hardness, and re-coated when needed, fills those irregularities, making it easier to sanitize or disinfect the floor surface.  Further (popular wisdom aside), a properly maintained finish is generally less slippery than bare tile.

Grout in a ceramic or stone floor is porous as well.  Leaving the grout unsealed is helpful, particularly in restrooms and lunchrooms; water spills, common in those areas, absorb into the grout so the floor dries faster.  But, in our hard water environment (I run a janitorial service in Phoenix AZ - we draw much of our urban water from the evocatively named Salt River), mineral deposits from spills and (more so) from damp-mopping tend to partially lock in the bacteria, protecting them from the disinfectant.  Periodic service, at least the way we provide it, includes machine scrubbing, generally with a light phosphoric acid, to remove the hard water deposits, improving both appearance and occupant health (the building occupant, not the grout occupant).

And, finally, when the windows get so bad that you can't see through them, and sunlight can't come in, safety suffers...

A bit about us:

My firm, CBN Building Maintenance, provides commercial cleaning services in Phoenix AZ and the wider metro area.  We've been in business since 1974; hold the BBB's A-plus rating; and have long been in the forefront of the industry in environmentally sensitive cleaning for health, safety and security.  Our program can generally improve Indoor Air Quality, in the size range of most allergens, by a factor of 50%, as reflected in our ongoing IAQ sampling.