Is it about having your personal writings accessible or is it making people’s writings accessible? An unsheltered person with a library card could write about themselves and that would be preserved on archive.org, copied by other/future archival websites, copied by individual data hoarding enthusiasts, etc. There is almost zero chance a notebook would survive any significant period of their life, let alone after their death. That record might become valuable insight to some future researcher that would otherwise have little information on the experiences of marginalized groups in that time and place.