Actually we don't need to gamble but gambling use to attract us because no matte how risky it is we still to put bet because of the easy money thingy it offers for winning.
In my opinion the gamblers want a short cut way to collect more and more money in just minutes, because if you earn money in real and regular it will take a long time to save some money, but in gambling you will lose your savings or win more money without spending any time. Thats why people gamble; otherwise I dont think that there is any need for gambling and not all the people gamble. On the whole gambling is not good from any aspect.