I once heard a man say, "If you want to hate your hobby, turn it in to a job."
While there is some truth to that, one should understand the difference between work and play. Work usually has a necessity attached to it, such as the necessity to earn a living, or repair one's home or car. Play usually has an aspect of recreation. There's no reason they have to be mutually exclusive, but there are some other factors involved.
Factor 1: Time Commitments - Play has no time commitment, work does.
Factor 2: Deadlines - Play has no deadlines unless it is a timed game, but even then, you end the game if you want to. You can't stay in business and tell a client, "Okay, I'm done."
Factor 3: Financial pressures - I realize some people spend a lot on their recreation (play). But, in business, you have to balance the income and expense sides of the balance sheet. In play, everything is an expense and wise people only spend money on play when they can afford it.
Factor 4: Customer satisfaction - There's no customer to satisfy when you play. In fact, you play to be satisfied.
Factor 5: Stress - Work can be stressful, while play is done to relieve stress.