In most cases someone drove into it with a tractor.
Now who in the world would do a thing like that?
Back in the summer a guy was pulling a four wheel hay wagon out of one of my gates onto the road. A 20' wide opening, two 10' gates actually. Anyway he hit the end of one of the open gates with the front of the wagon. It put a slight bend in the heavy duty gate (less than a year old) and pulled the bed half way off the wagon frame.
I was pretty mad but luckily it was his wagon and it didn't break the 10" post.