I don’t think these are really needed. I removed them in my (merged) manifest and the app is still working properly. The user should be the one explicitly including it if the app requires it.
I think whether you need them or not depends a LOT on which version of Android you use. We only recently stopped supporting 19 & 20. Just because you don’t need it doesn’t imply that no-one needs it!!!
Since we always need it, if writing external storage requires it, we should be the ones to include it.