"Office" hours

Who decided when office hours would be?

I can understand shift work. You need to get the next wave of guys in at a specific time to relieve the previous shift so as not to stop and restart the machinery. I get that.

But who decided an office should open at 8am? Or, even at the same time every day?
Who says that's necessary?

Bankers' hours are 9 to 5.
Why should anyone else open before that? No one can get to the bank before 9am to get money to spend as early as 8am, anyway.

On the other hand, why not open at 7am? or 6am?
Why not operate from sunrise to sunset? "Can't see the merchandise or read the forms? Then we're closed!" Think of the savings on light bulbs and electricity.

So, why are typical office hours 8am-5pm? Why?

Just a question.
Have any thoughts?