If someone sells alcohol to a minor they can be sued and will likely be in trouble if the child is harmed. It is the seller's responsibility to make sure they don't and it wouldn't enough to have a sign saying "please don't buy if you are a minor". They must actively check. Same thing with firearms. Even the (adult) entertainment industry works like that.
Here too tiktok "sold" a product to some kids, and these kids were harmed. Consequently they have some responsibility over that. Why should the IT industry get away with practice that would not be accepted in any other industry?
The role of parents is not to keep their kids safe at all costs. If it were then just keeping children locked up until their majority would be optimal parenting. Instead we as a society should thrive to make the world safe for those kids rather than just pretend it's the exclusive responsibility of their parents.