While I appreciate the sentiment, the OSM wiki specifically says[1] "In locations where the railway has been replaced by new buildings and roads, the mapping of such features becomes out of scope for OpenStreetMap. Historical mapping can occur on Open Historical Map."
(Just checked - OHM doesn't seem to have any data whatsoever - present or historical. Maybe I don't know how to use the interface, but all I see is land/water borders)
Right. In the two cities I have personal experience with, the tracks and/or sleepers are still there, just paved over. They are evident (and briefly verifiable) when potholes develop or roadwork excavations go into those areas.
Regardless of whether it's more suited to OSM or OHM, I just think it would be a neat feature to have on Open Railway Map.