i race at the track that the OP did and we do not run WGT anymore. the biggest reason was that the spec did not work at our track. the lilac tires made it difficult for even the seasoned racers to get a setup that was consistent. so the racers that we had consistently show up slow migrated to other classes. the problem with this is that if we were to "not" spec those same guys go to the bigger races and did not want to run a setup that would not be used at the big races.
we have a similar issue with rubber sedan at this point as well. the guys that run the class like spec tires. but not all the spec tires work at our track. now that there are other options for spec tires. they found a tire that works at the track and are used at some of the big races. but the attendance for rubber tc is low.
our most consistent class is 1/12 and i believe that the reason is 2 fold. first is that the class is raced nationally and we follow the "roar" rules. and second, those rules work on our track conditions. but the big thing that keeps the class stronger is that we have a core group that always race 1/12 and this group is competative on a national level.