Shitty programming isn't responsible for people hacking the game, that's just the opportunity. You need a motive, and it's the game designers that provide that. They needed a retention mechanism, and rather than providing a gameplay that is truly enjoyable on the long run based on its own merit, they chose an addictive micro-reward grinding/collection mechanism.
In such a setup, smartly-priced micro-payment is the only way to prevent the rich and busy from cheating. You would have thought that they learned their lesson with WoW and gold farming.