younger peeps are in the age of being curious in everything, like they really want to try new things that they see in social media even if there's a disclaimer that some contents are not suitable for their age that's why they need more guidance because they are prone in any bad thing that may happen. Influencers usually put a disclaimers in their contents that's why we cannot blame them because they just do it for the sake of money, however other influencers are intentionally display their content to catch up some viewers for their engagements.
Many kids have gone wayward in the mordem times due to social media, in some medias advertiding +18 rated contents have become very normal and most kids are currently gettng exposed to those contents including gambling as well since most gambling platforms use them or pay influencers to advertise their business. Well i don't blame those influencers though since they're doing their job.
It is the duty of those social media platforms to create policies that would restrict underaged people from creating an accounts with their platforms, you don't expect influencers not to do their jobs because their are underaged kids they’re not even aware of using the platforms and viewing their contents, the least they could do is advise underaged people from gambling and the effect it has on them.
And know why all this happens? Because parents sit in social media all the time in front of them. We can no blame influencers nor anybody for what kids do, as parents are the only one who are responsible.
I see you have said that its social media duty to create some platform restrictions. Actually there is today YouTube and YouTube kids where you dont get adult ads. But YouTube can not decide what your kid will look and what is acceptable or not. It will show popular average. In general, everything that is about kids - it is up to parents; its is their duty to check, monitor, restrict and teach.