Setting the parking brake is the law in California. Even with an automatic transmission. Also, it’s a good idea safety-wise.
" Also, it’s a good idea safety-wise."
And it is a good idea for the car. If there is any kind of grade the car can move downhill a little and put pressure on the parking pawl causing it to jam/stick.
( when originally posted, the OP had both 'brake’s spelled ‘break’, So I posted tongue in cheek ; )
I get a parking BREAK once in a while.
I’ll just lean back in my parked truck and snooze for a bit, setting the alarm on my cell phone so as not to nap too long. It was a great help returning to work after heart surgery.
During that time I’m always sure to set my parking BRAKE. 
( looks like someone was able to correct the spelling over the last hour, now 1:24 mdt )
I used to do that when I was on the force.
It’s a good idea to use it from time to time so when you REALLY need it it works and releases fully. The cable can get rusty from non use and cause your brakes to drag.