From our (STL maintainer) perspective, <array> includes <algorithm> because it needs equal(), <iterator> because it needs reverse_iterator, and <tuple> because it needs to provide get(). Minimal!

But yeah, it drags in a whole tree of headers. Minimizing this is possible, and we've taken steps to do so in the past, but it's a lot of work for possibly minimal benefit - user translation units tend to drag in many STL headers, especially if they're using precompiled headers like they should. We think our time is better spent fixing correctness bugs and implementing features.