Seeing how those sorts of things play out in actuality, it doesn't surprise me that unpopular or unprofitable products are killed rather than kept on life support. Lots of times, the people who would have to fight for them don't have the political will (or maybe even complete history of the product) to commit to staff allocation to keep them alive in the face of the alternative: chasing the next 10x dream.
Although depot migrations are tedious, the burden of doing them for all but a subset of mothballed systems would not significantly changed my life.
Off the top of my head I can only think of one time when an internal library deprecation caused a huge ruckus: some front-end framework was deprecated which led to a huge push to rewrite many of Google's internal websites.
When I left even BigTable, MapReduce and other services are still supported even though they have been deprecated and their replacements (Spanner, Flume) had been GA for more than a decade. (Although their API calls may just go through a translation layer, not sure.)