There are 3 legit reasons to have copy/paste 1.Huge buildings. 2. Laziness. 3. Just because you want it.
Only architects may copy and paste, heck if I was a designer with copy and paste I could have built my architect plot in 3 days. You must earn the commands before you can use them.
Architect isn't a cake walk, its a challenge. This is why there is only 10 of us. As I said before if I had copy and paste as a designer I could build my plot in 3 days. That's not a challenge.