Well, I did say one reason; there may be other reasons as well. The prime motivator, perhaps, is the desire not to alienate their user base. I can imagine that the price of advertisements for which WGT sells the space on these webpages, depends to a large degree on the number of daily visitors at WGT.com; and if a portion of these were publicly branded "quitters" in the discussion forums, they might stop using the site, reducing the number of daily visitors significantly, and thus also WGT's revenues.
So, it's OK for WGT to have a policy like this. Once reputation tracking is introduced and implemented correctly, all sides should be satisfied.