I have seen it happen many different ways, from USGA greens still having good soil structure on the bottom (below the thatch) to sands compacting. It was orignally thought that sands should never compact, but it turns out, sand isn't just sand, and some do. Add in wind or flood borne contaminents, poor choice of topdressing materials, etc. and the USGA started to point out that their greens simply may not last forever, perhaps to cover themselves.
As to topsoil greens still existing, I know there are many. They may be some of the most admired, but are also among the least played and highly maintained. And, they have probably been aggressively aerified with plugs removed and sand added back in the holes to modify their profile somewhat, even without rebuilding.
How well greens last is a combo of many factors, and its not a black and white USGA vs topsoil method type of thing. Examples exist all along the spectrum.