We know that earning bitcoins has become very hard now so we cannot afford to loose big amount of it in gambling as it will take long time to earn them back so its better to gamble for fun with a small amount that we can afford to loose as if you will gamble thinking of making profits then you will surely loose your money in it.
It is hard to earn bitcoin now because the price is high so in the past alot of site give their giveaway of over 0.001 btc, nowadays we only see them give less than 0.0005 because the price is high. I dont mind people that gamble with all those free money but atleast because it is free that means it is fine if they lose it
I think in different way even if its free I will prefer to save them and once it reaches to a decent level then will sell them and make money out of it as in gambling I am pretty sure that I will be loosing everything that I have so I will not waste them in gambling even if its free.