Homeowners with pristine lawns have a phobia of any machine on their grass. I've many times been questioned. "Wouldn't a six inch deep 2" wide trench be enough?"
I go into my explanations of why deeper electrical conduits last forever. Mostly, I never hear from that customer, until the other guy installs conduit 6" deep in a 2" wide trench, and it fails in the middle of winter.
Christmas time I got a call on my answering machine Friday evening. A subcontractor for Comcast had ripped up a 50 year old feeder to a mobile home. Dark of night, I made temporary repairs. I told the property owner "It is ESSENTIAL that you replace this feeder this coming week before the ground freezes any deeper!
I was ignored.
Two weeks later: I still don't understand why another subcontractor for comcast was there again. You guessed it! They too plowed up the same feeder! This 150' long cable ended up with 8 patches in it 5 of them under the driveway!
Maybe I'm obtuse, A conduit buried as deep as code requires, deeper in cold climates will NEVER fail. Why torture yourself, and your electrician burying it 6" deep?