aside from the fact that gambling advertisement might be banned for certain countries across the world its also probably due to the fact that advertising on TV will not give the gambling sites themselves targeted audience.
I think TV are mostly just some people try to enjoy shows not betting, quite opposite if we are talking sports, its quite effective thats why in football matches the gambling ads are everywhere because its targeted audiences I think because surely in every match some people want to gamble.
Advertising on TV might be banned but we know that the internet now become more advanced so kids can watch it for free from their social media page. They will see it many times every day without control unless we use some adjustment to their smartphone or we gives understanding to them that playing gambling can gives a negative effect to their life. But yes, people enjoy watching the matches and not about betting so they wants to search an entertainment rather than to place a bet. And nowadays, the casino tends to use the internet to promote their business whereas they can get unlimited potential target from all countries. It's a responsibility for every people to be able to respond to what happened and will not take a wrong way.