It's not just NIH, after a certain size every external lib is a liability. You don't want to wait for some OSS maintainer to unblock your multi billion dollar business' issue.
Re:We Halved Go Monorepo CI Build Time
by ByteJockey on Sunday June 26, 2022 @02:37PM
(#31886618)
If that were the case, you'd expect to see forking of 3rd party libraries rather than writing of new ones.
Most of the time you probably only use a small portion of the 3rd party library functionality so forking the whole thing and ripping out everything you don't use or maintaining it doesn't make much sense.
But when your team owns a repo, then at least the damage is contained within your team.
Google solves that problem with heavy NIH syndrome (its hard to get promoted by utilizing an external third-party lib, better develop your own), and writing tests, yes. And for those few third-party libraries that google still depends on, updating them is a big PITA.