My first guess with this would be: they were read-only, then they wanted to post something or write a reply to someone and at the time considered it to be a one-time thing and created sort of “throwaway account” for that specifically, but then they kept visiting the place and it kind of just stick with them. Yet again, my guess might be completely wrong. But at least this is one of the possible motivations behind such accounts.
My first guess with this would be: they were read-only, then they wanted to post something or write a reply to someone and at the time considered it to be a one-time thing and created sort of “throwaway account” for that specifically, but then they kept visiting the place and it kind of just stick with them. Yet again, my guess might be completely wrong. But at least this is one of the possible motivations behind such accounts.