You will find tons of players needing to gold wow classic purchase vanilla career materials, for instance. There are also some bis consumables that use vanilla herbs.
The only alternative that they are not ever likely to consider is to reset everyone's gold, mailboxes, the auction house, banked and bagged items leaving only the BoP ones.
And the biggest reason not contemplate it, is that unless they follow with a severe attempt to halt gold buyers/sellers, then affect only hurts honest players.
Almost 80% of the new folks we take in appear to turn out to be gold farmers. (I feel that the gold farmers are more prevalent as they use WoW for a job and rebound between scripting and actually controlling their toon) We've never gotten some kick backs from such personalities but we usually take just two raids to figure out they're gold sellers to have the ability to kick them from guild.
I had the exact same tinfoil hat type of buy wow classic gold conspiracy but I have given up on that storyline. Reason being is I'm in a semi hardcore guild and in this stage in classic it is very tough to discover new people coming raiders so when a few unguided 60's desire in to get a trial ridden place we are made to try them out.
However would they willingly get rid of 1/5 of the participant population when they can continue to make millions from individuals abusing their imaginary currency for real cash. From a PR perspective it is the biggest shit-filled slap in the face to the player base, from an economical perspective it is the simplest money they'll ever make.