Having played Legion for a month and got bored and didn't like the way progression is tied in to forcing you to do things you may not be in the mood for e.g. Mythics, I thought I it was time to unsub before they took a payment.
Then it dawned on me how fortunate for Blizzard that people are still willing to pay a sub for a game that should clearly be Buy to Play (based on what you actually get for your money). They charge full price for each expac and really and truly, that should be enough of a cost for what you get. The patches are not worthy of a sub or price (and happen all too infrequently) and like many games, should just be considered as ongoing story/development to give people a reason to keep playing (and having the opportunity to buy stuff from the WoW shop) until the next expac.
There is a lot of value to be gained out there from other Buy to Play games, but I guess all the time Blizzard have people paying subs, it's a model they will stick with. I'd carry on playing WoW if the subs dropped as I could dip in and out as required, but paying a sub makes me feel obliged to play but I'm bored of logging in regularly now so made the decision to stop.
Few games would get away with a sub model these days, but all the while people are willing to pay, they will charge you for it.
I know I said blizzard are fortunate, but yes, you make your own fortune and I am not questioning people's desire to want to pay a sub so they can play the game, which they must be enjoying. Perhaps it's like a drug for some, who can't let go, who knows?