There were high hopes for Plants vs. Zombies 2, but when the game finally launched it became clear that the free-to-play gambit hadn't paid off. Well, it paid off in the sense that a lot of people probably spent a lot of money on it, but at the expense of any semblance of a functioning in-game economy.
The keys required to earn new plants and other upgrades were incredibly rare, and the only reasonable way to get more was to spend real cash. Meanwhile the coins used for purchases in the first Plants vs. Zombies were all but useless in this iteration.
Thankfully the game received a massive update in December, an overhaul that eliminated the need for keys. But at what cost?