Another reason to use ALT text which some people might not have considered: it benefits people who are not visually impaired as well.
As #Mastodon is #decentralized there is no central network hosting all of the images. Should the admin of a server decide to purge old images to save space, users accessing older posts will not know what an image was without an ALT text.
Take this post from 2022 for example.
André Polykanine reshared this.