Some of these -- the domains for the federal government's executive branch -- were already public. This includes the rest of the federal government (e.g. Congress, the courts), as well as all the .gov's in states, territories, counties, cities, and native tribes.
There's about 5,300 of them.
More cynically, I've noticed that it's a relatively benign form of hoarding. i.e. I get the quick dopamine rush of "oh this is interesting, now I have it" without, say, crowding up my living space with trinkets. With an abundance of storage that is essentially invisible to me when I don't want to think about it, I can keep what I want, when I want; often while fully aware that I'll never look at most items individually again. I think of it as a kludgey form of external memory / internet butterfly collecting. The only downsides I've thought of are: time frittered revisiting archives, the (small) transaction cost of tagging and placing items into the archive, and the externalized costs of maintaining the hardware.