While watching TV with my kid, I've watched various advertisements of gambling nature (let's say for example, Rummy123, RummyCircle, A23 Rummy, etc.)
These are all specifically Indian ads, but I'm sure you may have seen various gambling advertisements, some banners at boundaries when cricket is ongoing, even in any other sport. How would a kid ignore those things, they might just come and ask you about what is it. Till when can we lie to them? Don't you think that the frequency of such ads must be less in order to let the kids not get trapped into gambling and don't do it at such a small age?
The laws regarding gambling in different countries vary, advertisements of a gambling nature can be shown on television in countries where they are permitted (Legal). In several other countries where gambling is considered illegal or does not have permission from the government, gambling advertising may not be permitted. Maybe the gambling site you see on television is a sponsor of that sport.
Tell your child the truth. Tell your child the truth, lies will make him respect you less when he knows the real facts. If you don't want your children to get caught up in gambling, avoid them from anything related to gambling.