This has been Starbucks policy (though perhaps unofficially) for years. I worked my way through college at Starbucks and stayed there for a short period of time after I finished.

Shift supervisors were required to be available 100% of the time, and hours weren't guaranteed. That meant being available from 3:45 am to 11:30 pm seven days a week. It wasn't uncommon to be scheduled for less than 30 hours per week and very rare to be scheduled for more than 35 hours per week.

Regular baristas didn't have it much better. They were allowed more flexibility with their availability. However, they were regularly scheduled for 19 hours per week, thus ensuring they wouldn't hit the 20 hours per week required for benefits.

I don't mean to be entirely negative, Starbucks got me through school, and the lack of hours was a great incentive to go out and find a real job instead of wasting more time there.

One underlying weakness in the Starbucks model was that it made growth promises