Its a constant game of cat and mouse with most things of this nature; ad blocking, spam/scam bots, etc. Admin finds a particular string of scams, adds it to th

Its a constant game of cat and mouse with most things of this nature; ad blocking, spam/scam bots, etc. Admin finds a particular string of scams, adds it to their checker. Scammer gets blocked. Scammer changes wording, starts again. Rinse, repeat. Add to that, that many sites are not designed in ways that prevent signing up multiple times, and you get the ability to create botnets with ease. Also, spam accounts for -so much- traffic and posts, that companies would lose large portions of their userbase by just blasting every scam/spammer away in one go, which looks bad (in their eyes). Not-so-fun fun-fact: Spam email accounts for 45-51% of all email transit. While mail is pretty low byte count, simply killing all spam mail would leave places like google mail with half their infra unused, which again, might look bad in their eyes