I guess the issue there would be, why label any particular stretch of an interconnecting network of shafts "7" or "2" or "3" on the outside
? It apparently tells nothing about where this particular lift goes or cannot go - as far as we know, all lifts go everywhere.
Clearly, it is unlikely that all the doors marked "Turbolift 7" could be along the same vertical shaft, or along the same circular or radial horizontal shaft. If they are along a stretch of shaft that swerves and weaves through the ship, why is that stretch being given a number? Why not call it the sum total of radial shafts 2, 17 and 9, circular shafts 3 and 5, and vertical shafts 1 and 8? It is unlikely to be a single "unit" of shafting for any user anyway.