I can't speak to other projects, but I know the additional pieces of tooling I add to my buildchain are there to automate tasks that are otherwise undocumented/uncaptured and thus easily forgotten (Joel Test, step 2). On a team of ~50 core committers and ~100 intermittent committers across the globe (which isn't that big compared to other teams), if it doesn't have a CI build running and passing regularly, it will eventually break and stay broken. Examples: code generation, database schema generation and checking, dependency compilation, building artifacts. Other pieces of tooling I add to orthogonalize and amortize common tasks, e.g. Dagger2, Immutables, AutoFactory.
Again, I'm not familiar with flavor-of-week web dev stacks and I'm not defending all of it, but there are clearly steady-state benefits to tooling, even if the initial setup often ends up being a maze because it isn't in the critical path of core developers.
I think there is huge benefit to be gained from projects considering the aggregate bootstrap effort required to get the whole stack running. But I still think this fragmented, modular approach, even with the downsides discussed in this thread, is better than the likely alternative: depending and waiting on a company like Microsoft to deliver a monolithic development environment for which a Product Manager has spent literally years crafting and honing the bootstrapping experience before release.
EDIT: wording