In Hearthstone, the rewards for daily quests dwarf the rewards for any other in-game activity. You get 40 to 60 gold per day for completing a daily quest. The only other repeatable way to obtain gold is by winning games against real players for 1 gold per win. Thus, a single daily quest is worth at least 40 wins or roughly 80 games, assuming a 50% win rate.
Some players have started complaining about the rate that gold is obtained. They want the 1 gold per win to be increased either directly or through extra rewards for win streaks. Some players have even called for a gold reward for lost games as well. I am not sure how I feel yet on the matter, but I believe there is a good reason why Blizzard chose to set it up this way: World of Warcraft (WoW).
World of Warcraft still has millions of subscribers. Those players are the primary audience for Hearthstone. Because they have to pay money for game time, they spend most of their free time playing WoW over other games. That includes Hearthstone. Blizzard saw this and needed a way to make Hearthstone appealing to that large playerbase.
World of Warcraft is a massive time sink. Most players can put as much time as they have into it and still not do or see everything. If Hearthstone were a time sink like WoW, the WoW players simply would not have the time to get new cards at the same rate as the majority of players, and the majority will definitely be free players. Blizzard has fixed this potential problem by essentially limiting the productivity of your time in-game to 1 or 2 hours every day.
Players can of course play more if they enjoy the gameplay but will get no more good rewards until the next day. Some days a player might be just a few gold away from the 100 to buy a booster pack and decide to play more. Also, as a player increases their collection, there are many more card combinations to try out. However, for most days and most players, there will not be much incentive to play longer after the daily quest is finished.
Hearthstone will not be a typical Blizzard game. Consumers will not pay $60 upfront and get full access. Instead, they will logon a little bit every day slowly collecting about 15 cards per week, or they will pay a little money every month to keep things moving along. It is a typical free-to-play game. If a player wants it to be their primary game, they will need to spend a little money each month to keep the game interesting for long hours. If a player wants to play for free, they will have to play it as a casual game.
For those angry over the game’s monetization, understand why the game is designed this way. If your style of playing does not fit with the styles Blizzard is catering to, there are plenty of other card games that may. For example, Scrolls is a game made by Mojang that goes with the upfront payment model. You pay $20 to get a free deck, and then earn cards at a much quicker pace than Hearthstone.