I think gp's point is that nobody does this in an organized way that's not tied to a platform. When Facebook and Google eventually die, their archives will die

I think gp's point is that nobody does this in an organized way that's not tied to a platform. When Facebook and Google eventually die, their archives will die too. You'd ideally have some format with the openness and durability of an ASCII file that could be stored in a single location and survive multiple storage medium migrations trivially; something like a photograph in a box, which anyone can interact with easily regardless of whether the camera maker is still in business. And while a GitHub or Dropbox sounds great, the issue is that most people don't have the technical ability to collate their data from all the places its stored, and their descendants also mostly won't have the ability to pore through it unless it's pithy and organized--and if that's the case, then that it just means that the deceased came up with their own ad hoc durable "life archive" data format.