Perhaps you have a point there. By banning smoking advertisements the tobacco industry did in fact get hit by a large toll that they were not expecting and the young people did start smoking less. But that might just be a subjective view of the banning ads sitation, which might not be applicable to the gambling world. Gambling, while harmful to your mental health and wallet, might not be seen as great of a danger to merit a full advertising ban.
I don't know where you're from, because as I know it, gambling ads are freely shown during football games, and other sporting events in the United Kingdom. That's why they don't want celebrities and sports stars in advertisements connected to casinos and gambling.
I believe gambling ads are even banned entirely in some countries.
As far as I know, the number of countries where advertising gambling is completely prohibited is quite long.
I think the restrictions that are being introduced in England are just a step towards getting Britain on this list as well. I think that the government of UK, due to the fact that the gambling industry there is huge, wants to introduce such restrictions gradually so as not to provoke too much protests from bookmakers.