[rasmus-kirk]

But they can't legally purchase/access it without the involvement of an adult, unlike social media. You could argue that the parents sanction social media use by giving their kids a phone/computer without any sort of parental controls, but most parents probably have neither the resources nor proper knowledge of how to sufficiently provide a safe platform for their children.

[RobotToaster]

You can't legally buy a mobile contract in the UK if you're under 18. So in most cases the parents did buy it for the child.

[gambiting]

You are aware that pay as you go sims are available from literally every store in the United Kindom, and any child can just buy one within minutes if they are so inclined?

Not to mention that using social media does not require a phone number, and wifi is practically ubiquitous.