There are two (2) types of gamblers: first is the one who chases for profits; the other is the one who finds it purely for entertainment.
Actually there are more type than that.
Some gamble due to curiousness, other for social benefits and more.~
I don't know, can't all that be labelled as entertainment? I mean, I agree with qwertyup23, your goal can be either getting money, or getting entertainment from gambling. With this simple classification we can easily separate what's wrong from what's right.
When you started spinning slots with entertainment purposes in mind, but in the process of the game, after losing $20 you suddenly want to win it back, you should know you are stepping on the wrong road.