This has been approved on sandbox
I am a place of joy for the kids.
I make the job easier for adults with certain jobs.
I am a tree.
For the kids, I'm made of a lot of small pieces.
For the adults, I don't exist physically.
When I'm a tree, I can grow up to 60m and explode yearly.
That has been my life so far, but lately, I became a rule also.
What am I?
[Edit - after the question was answered: may contain spoilers]
This is part of my protest against sandboxing riddles. Same as this one