The old Legos. Where you got a bunch of bricks with no plans and the only limit was your imagination (and the quantity of bricks).
Of course children like it, just like they liked the original Legos.
And by the way, why children only? I'm playing on a semi-private (need to apply and be accepted by admins) 18+ builder's server on and off.
There are such things.
To be snarky, if you want an environment without dicks you should play on an adults only server. When we play, we're too busy building huge elaborate buildings and terraforming large portions of the landscape to build measly dicks.
But also, MC is simple enough that "a dick" is five blocks in a particular organization... and it quickly becomes boring, not to mention uncreative. Building dicks isn't as fun as Everything Else in the game.
[1] http://habitatchronicles.com/2007/03/the-untold-history-of-t...
Minecraft is very much NOT just like the old Legos.
https://brickipedia.fandom.com/wiki/Automatic_Binding_Bricks
were the old Legos. You may notice that the instruction booklet has a striking resemblance to basic Minecraft building...
... or is it the reverse?
Still, although there's no set goals like in other games, this style of game has to have "affordances" for goals. Even the building activity in MC is not "free", as monsters are there to get in the way of the players' projects.
I also think that the social aspect is crucial, in the sense that having fun building things doesn't last, because one eventually runs out of ideas. Showing to others what you have achieved is an important part of it. Does art exist without an audience ? [2]
I think it is interesting to note that the fact that MC's world is fully editable by players is what drove the choice for the voxel technology, which was the only one allowing it with a normal PC at the time.
[1] https://www.luanti.org/ [2] https://thehoya.com/opinion/eye-of-the-beholder/
But not everyone likes to play in the sand but those that do, really do!