No-raised floors (normal floors) are common in ISP and co-location (CoLo) data centers that have cages for different customers
These have no subfloor space for cables or air conditioning, but they have certain advantages
The wire-fenced cages go from floor to ceiling and each cage is rented to a customer
The absence of floor tiles removes the possibility of illicit access by someone removing a tile and crawling below the tiles to a neighboring cage rented by another company