I literally checked which profiles have "Never" as their last active date, like I mentioned in the OP. I don't know if that's entirely accurate but it seems unlikely that so many users would just register and never login for some other reason.
While majority of those accounts might be inactive due "evil fee", there is one very active group that is constantly using old accounts with no prior posting history,
Vitor Services and I guess some of those might be theirs, waiting to be activated. They sell thread bumping, and for some reason they prefer using old accounts and every time those accounts get tagged or banned, they just replace them with fresh batch. It is like they were thinking in advance and years ago created thousands of them, and then just activating when and if needed. They are probably still creating new ones.
For example, you can find those accounts I am talking about currently active in these two threads. Accounts created in 2018, no activity whatsoever and then suddenly waking up few years later and going straight to "work". If those get tagged they wake up new ones, rinse and repeat.
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