Where I play (Misery EU) turtles are very rare on both sides.
Yet, sometimes I actively lead my team into turtling to "teach the horde a lesson". This occurs in games where the horde has an utter majority in twinks/19's and is camping our GY/ letting nobody past midfield. The best you can do then is go full defense, and atleast get a few kills that way and piss off the horde, IMO...
I may have just played the my first match where alliance didn't turtle!