A lot of MMORPG actually have gambling elements involved, I think that it's not simply the thrill of victory that is the rationale behind gambling, but instead the thrill of potentially winning a life-changing amount of money, something which can't be done on online games through simple gambling.
Many people are gambling addicted and they only gamble online or in regular casinos. Playing games on computer are of no use for them. Although your suggestion is very good but regular and addicted gamblers will never follow it. I also like online gaming because I am not regular gambler and I only gamble seldom for fun and entertainment. I dont like online gambling.