~snip~
Yes you are right. I am also think with the same way that gamble isn't any bad think. Yes it's convert to bad when one person got addicted on it . I think not just gambling but over-indulgence has a bad effect on everything. So in this way gamble should be in self control and also it's purpose should be only entertainment which already mentioned by op.
I think it doesn't matter whether a person gambles for fun or for profit as long as he gambles responsibly, I believe there will be no issue ahead. The problem with people who gamble for profit is that they failed to set up a limit on the fund they have to spend resulting in spending money that is allocated to households expenses. There are lots of cases where a gambling have to sell everything in order to recover what he has lost because of being irresponsible while gambling.
The problem is that a player always thinks that luck will come and this thinking can make the player lose control and use any money as long as he can continue to play and hope that luck can be obtained and the money he has spent before. Never chase luck, let alone the desire to recover from defeat, let go of what has been lost, and play if you already have the money to be able to play.