This website made me reconsider if 99.9999% SLA and always online is really that important for lots of websites. I used to self-host my own server in my own apartment, but gave up on that after my internet provider had their first major outage that lasted almost a week. Also I didn’t want to worry about the fire hazard, or the server going down when I was traveling etc.
But a solar powered server seems interesting, if the batteries could be made fire safe.
It’s not like those major social media sites don’t have some kind of data center (or rent one) in every “major” (population wise) timezone they operate in. Your other arguments still hold true, but I think even then it would be better for all of us if those websites went down every now and then.