I get this impression the ones refusing to blacklist either don't know that the blacklist feature is in the Settings, are too lazy, or they're sick and tired of e621 they want to get banned on purpose.
I'm using the RE621 plugin, which is a breeze on desktop, but a hurdle on mobile. One neat feature is on the Post page, where you can can blacklist any tag on the list.
My wishlist is make the "Click to Blacklist" feature a main feature for e621.