I deleted my FB account years ago, so this might have changed... but it's even less straightforward then you think. Instead of burying the "delete account" option in settings, they hid it entirely. You could find "deactivate account," but permanent deletion was only accessible if you knew the URL. Even then, Facebook kindly imposes a 30 day delay before deleting your account; if you log in in any way, even accidentally, before the 30 days pass, it resets the timer, reactivates your account, and you have to start from 30 again.
Instagram had a similar problem when I deleted it a year or so later: you couldn't delete your account from the app. You had to log in via a browser, navigate the very dated UI through to advanced settings, and request a deletion there. A lot of folks don't even know their Instagram password -- I think they just used SMS codes originally -- so it was surprisingly hard to get a password associated with my account so I could even log in via a browser!
Instagram had a similar problem when I deleted it a year or so later: you couldn't delete your account from the app. You had to log in via a browser, navigate the very dated UI through to advanced settings, and request a deletion there. A lot of folks don't even know their Instagram password -- I think they just used SMS codes originally -- so it was surprisingly hard to get a password associated with my account so I could even log in via a browser!