I can’t tell what practice you’re referring to. Are you perhaps referring to older wiring that connects large appliances to a neutral and two hots but no ground, e.g. NEMA 10-30R receptacles? Those indeed suck and are rather dangerous. Extra dangerous if the neutral wiring is failing or undersized anywhere.
But even NEMA 10-30R receptacles are still 120V RMS phase-to-ground. (And, bizarrely, there’s an entire generation of buildings where you might find proper 4-conductor wiring to the dryer outlet and a 10-30R installed — you can test the wiring and switch to 14-30R without any rewiring.)
The exception for residential wiring is when the neutral feed from the utility transformer fails, in which case you may have 240V phase-to-phase with the actual Earth floating somewhere in the middle (via the service’s ground connection), which can result in phase-to-neutral and phase-to-ground measured anywhere in the house varying from 0 to 240V RMS.
> wet bathroom floor
A GFCI receptacle adds a considerable degree of safety and can be installed with arbitrarily old wiring. It’s even permitted by code to install one with no ground connection as long as you label it appropriately — look it up in your local code.