As a brand new entry into the hobby, I have stepped in expecting that everything is set to YMMV.
To some extent, I believe that this helps gents remember that each lady has rules that need to be followed. Additionally, I have found that the ladies I am interested in seeing are very good about posting clear rules. I do not expect the maximum simply for meeting the minimum, but I at least know the minimum that will get me into the door.
YMMV reminds us gents that attitude + approach continue to mean something. YMMV should remind hobbiests on the customer side that they shall participate as a Gentleman. With this, providers shall conduct business as a Lady.
Providers who establish YMMV as a push to get a client out the door quickly need to remember that the client has the strength of posting a public review.
Noting the above, I believe that YMMV is a very mutual benefit.