Because like most of my friends then that do engage in gambling, they didn't even know they where getting addicted until they started seeing the effect, I see some of them then gambling daily , and even when they are losing they kept going , having the mindset that no matter the losses they will surely endup with big wins . Till they finally realise that if they continue like they might endup ruining themselves.
Because gambling is exciting, especially when they are on a winning streak they will forget everything but in the end the inevitable happens and they start to lose everything and then they feel bad and miserable. They wish it was that easy to stop but the thrill is what keeps them playing, they often think life would be much easier if the internet had never been invented. because at first they are quite sure they will not get addicted, but often over time gambling makes them addicted. Therefore it is important to gamble with strong control, be it emotions, psychology and of course financial control so that addiction can be avoided.