I don't remember the age my kids first got Lego's but they built a lot of stuff.  Later in life one worked for a company that made Lego robotics and got to go to Denmark several times.

I had an Erector set from the time Santa brought it and learned that a screw driver can punch a hole in your hand.  I learned that getting your fingers in gears can cause pain and blood blisters.

My set's part were  put together with nuts and those blasted slotted screws.  The power to run things was from a 110 volt motor with multiple gears and PTO shaft.  Prepared me for working on a lot of machines later.