I don't know where you live, but what you're describing is not the norm in any developed country I've visited. Hourly jobs come with a schedule. You're expected to be at work for the entire scheduled shift, it has nothing to do with amount of work to be done. If you just decide to leave halfway through your shift, you will be fired.
As an aside, if you were paid hourly and only worked a few hours a week, you wouldn't make any fucking money. That's kinda how hourly compensation works, you have to BE AT WORK for an hour if you wish to be paid for that hour.
Got any more dumbass fucking shit to say? Get bent.
TheDudeAbiding