I don't believe that Gambling helps Bitcoin in anyway , If someone joins the bitcoin community just for gambling then sooner or later he will lose everything and probably leave the community.
People should see Bitcoin from another perspective and not only as a gambling or a Darknet tool.
Well, more than 50% of the total transaction volume of Bitcoin is gambling related. That's a fact we can't deny. But yes, I also agree with you that Bitcoin is more than a tool for this purpose. Will people leave that lose all their coins with gambling? Maybe, but sooner or later they will come back as Bitcoin stays in their system. They just need to make sure they stay far away from gambling.
Seriously addicted gamblers lose everything, but most of them only gamble a small amount each week. Casinos using Bitcoins would bring new people into the Bitcoin community, and most of them wouldn't lose all their coins with gambling. Most gamblers lose, or the casinos wouldn't survive, but most gamblers only lose a small amount and keep gambling.
If you as an occasional gambler with only small amounts can keep this up without going down deep with large bets, then the losses you experience will stay small. It however requires a good amount of mental strength in order to not turn into a gambling addict. Not many people have enough self control to stop when they are losing.