ClubWPT is subscription based poker room. Players don't have to deposit money in order to play. That's why there are no real money ring games in the poker room. And that's why it's impossible to get rakeback here.
All tournaments with real money prizes don't require players to pay money. There are special Tournament Points. As you see neither ring games nor tournaments require real money buy-ins.
There is no Rakeback because players don't use real money in ClubWPT and thus don't pay rake. How can a poker room offer rakeback if players don't pay rake? It's impossible.
Though there is no rakeback, each player can win very good prizes. For example you can win WPT Live seat! It's equal to $10 000! In real-money poker rooms average player spends a lot of money every month for playing ring games and tournaments. In ClubWPT VIP member has to pay only monthly subscription to be able to participate in all promotions of the club.
Rakeback is a kind of extra reward for players in real money poker rooms. In WPT Club the prizes are really big and you can get amazing valueback without rakeback.