Playing for fun is the initial expectation from every gambler to do, so that we don't get ourselves into other things else beyond our capacity at the cause of gambling, also, our irresponsible gambling nature does not make any difference to the casinos if we choose to be a responsible gambler or not, it does not affect them either way, but we are the one being affected, because we will be missing out on other things so important in life we could have enjoyed, if we are a responsible kind of gambler.
You are absolutely right, playing for fun can actually save gamblers from a lot of trouble and the gambling industry would not make a lot of profit like what they are actually making now...although they don't really push anyone to get addicted but they get their profit from gamblers that chase profit...in order to make sure that you don't Step out of line or go beyond your limits it is better to gamble for entertainment only