If this question is against the new policy of deleting or not allowing children to have profiles - you can blame the EU for that new policy.
As per the new GDPR rules that the EU enacted in May 2018 (less than 2 months ago), wikitree chose to delete profiles of ALL children under the age of 13 and to make UNLISTEd all persons currently still living.
These policies were discussed for several weeks before this event so we knew it was coming. (Discussions began in March or April)
Until we know how much the EU will enforce any rule breakers, we have to be safe and follow their rules.
If the EU ever shows a softening in their application of the rules, then WT may be able to lighten up - but until then we must follow the rules.
If WT ignores the EU rules, then WT is liable to be heavily fined - and since this is a voluntary organisation, WT wont be able to pay the fine and may be forced to close this website down.
As to why the EU rules affect us when most of us do not live in Europe - the GDPR applies to ANYONE WHO COULD POTENTIALLY become an EU citizen - which basically means everyone in the world.
The sooner you accept that we keep the children off WT for their privacy and safety, the sooner you can get back to doing genealogy.