If I had paid for a full pass I would expect TOTW included.
It's probably more of a logistical issue more than anything - they can only have a limited people going up there with bikes due to the lift situation and they wouldn't want season pass holders taking up 90% of the spots everyday without paying extra $$. Definitely sucks though when you already pay $600 or whatever for the seasons pass and then gotta pay $15 every time you want to ride TOTW.