It is true, the restrictions imposed by gambling platforms do seem to be just a formality, that's why I think the government should be more assertive in enforcing its regulations regarding gambling. The government has the full authority to compel casinos to update their systems, making it difficult for underage children to make deposits. The government can also deploy financial institutions to monitor every transaction. I think all of this is easy to do because the government has the authority. Furthermore, parents are also responsible for guiding and educating their children, and should also limit their children smartphone usage.
Platforms can't prevent users from registering for their services. All they can do is perform KYC. That's why many online casino platforms implement KYC. This is also part of a government-mandated effort to reduce underage users, as well as to prevent money laundering and other crimes. Similarly, third-party platforms can't handle ads if users provide false information, such as stating they're over 18. If ads end up appearing on the account of a user who is actually under 18, it's not the platform's fault, but rather the data they entered was false. Therefore, while governments and service providers can only anticipate this through regulations, the user is ultimately responsible for complying with or violating the regulations.