Excluding minors is a product decision.

For an independent developer or a small team, including minors as users looks harmless. The product may be educational, meant for ages 16 and up, or have no apparent link to age at all. The problem appears when that decision meets the law.

Laws that protect minors are varied and strict. In the United States, verifiable parental consent is required for children under 13. In the European Union, the threshold goes up to 16 depending on the country. In the United Kingdom, the children's design code reaches any service likely to be used by people under 18, even one not built for them. On top of that come parental controls, adapted policies and, in the app stores, dedicated programs with their own rules on ads and data.

App stores are starting to help in the other direction. Google Play offers age-range signals that an app can use to restrict sign-up or certain features. In some jurisdictions, acting on those signals is already a developer obligation, not an option.

When teenagers are not the majority of the target audience, leaving them out cuts legal and development costs without losing the users who sustain the product. The exclusion has to be real. The product is declared 18+ in the store and in the terms, and access is blocked when the platform signals that the user is a minor.

Every product has its own audience and exceptions. Requirements are worth confirming in detail because they vary by country and change often. What holds is that including minors is a decision with a cost, and it is better made explicitly.