About those "parasitic" altcoins that live on the Bitcoin blockchain

At the start of February we had 10,000 bitcoin nodes. Now we have 8,500 and still falling:

I know all the reasons why people might stop running a node (uses too
much disk space, bandwidth, lost interest etc). But does anyone have any
idea how we might get more insight into what’s really going on? It’d be
convenient if the subVer contained the operating system, as then we could
tell if the bleed was mostly from desktops/laptops (Windows/Mac), which
would be expected, or from virtual servers (Linux), which would be more