Earlier quoted context omitted.
I mean, I think the answer to this is the very simple: they think it will lead to more money. I'm sure someone in a board meeting saw something about GrapheneOS and LineageOS and Cyanogen and feels like if they de-open Android, some (or most) of those users will move to vanilla Android, and that will lead to profits. I'm not saying that they're right about this; I think ultimately very few (if any) people actually kn…
I don't have exact numbers, but I'm sure Graphene, Lineage, and all of the mods combined are much less than 1% of all android users; as well as these customers being less profitable than average as a marketing target. Posting this from my lineage phone.
That said, there might be stuff that's actually using open source Android for profit. For example, the Nook Glowlight Plus, which runs a modded version of Android, doesn't appear to have any direct or even indirect references to Android anywhere (and I had to contribute a bit to the discourse to even get the rooting to work [1]). I have no ideas about the inner dealings of Barnes and Noble, but it wouldn't surprise me if they're running a completely forked version of FOSS Android and aren't paying a dime to Google for it.
I suspect these are the things that Google is trying to crack down on.
[1] https://www.mobileread.com/forums/showthread.php?t=360563&pa...