It's not going to stop gamblers and it's not going to stop streamers. Pretty pointless if you ask me.
I don't see it's about banning gambling streamers but it about going against crypto casinos. Obviously platform like Google and other giants (I guess Twitch is only a small one so far) don't want crypto to have establishment of crypto over their government controlled fiat currency. Most of the time it's the pressure from government agencies and these companies are just saving their business so that they can survive.
But as @coolcoinz said, that will not stop gamblers and streamers from creating content about gambling because many other sources can still accommodate it.
It is like a war between the good and the evil because the government wants to protect their people from the danger of playing gambling
But whether they will play gambling will depend on how they can be responsible for what they do so they do not get a bad impact from gambling.