[blawson]

I wonder how much of this can be traced back to the proliferation of System Design interview stages, and resulting training material?

From my experience all of these resources tend to direct you to think in microservices / uber-distributed architectures. I can easily imagine this causing folks to consider this as "the way we do systems now" and taking it to extremes.

The low barrier as well for 1 engineer to decide they want to just get busy on a weekend on their own and build something is another way I've seen this proliferate.