We can't protect kids from looking at ads in town on the way to school or tutor. It won't be practical to rely on filters because they aren't 100% reliable in most sites. Ad blockers break sites so they aren't the best way. You'll have to sign in for youtube & others for kids but how many ppl do it ?
We can filter the ads that comes out in the gadgets of our kids if we want them not to see any of these. But it depends also on which content that the kids are watching nowadays. If they're the contents that are just for kids, I think they're just fine and there is also the YouTube kids that they can use so that each ad is filtered there and probably no gambling ads are going to come out from there. What we have no control is the national tv that we are sure that we've seen some ads popped during tv shows and when they're on the ads but these kids don't know what exactly these gambling ads are.
I don't know how many but some probably are when they are valuing the protection of their kids from the adult contents and the other contents that are inappropriate for the kids. The penny that they pay for the subscription monthly is worth it for them and that's why it's a way to protect their kids from such contents. While we can't protect them when they're away from us and when they're going to somewhere else, it's best not to allow them with gadgets outside the house to monitor the activities that they're doing on that gadget.