Why am I not allowed to work part-time?

[jstnrgrs]

At my last job, I worked from 3-11:30. But the next shift arived at 11, and it only took about 5 minutes to hand everything over. After I had been working there for about a week, I started going home as soon as I knew everything was all set (11:05-11:10ish). Some of my co-workers complained because they stayed while I left, but I just said if there is no work for me to do, I will leave.

My current job is a day job with no strictly defined hours. I work when there is work to do, and I go home when its done. I think that if I wanted it to be part time, I could arange that, though I don't know how the benefits would translate, and it would kill any upward mobility that I have.

I can't stand sitting around doing nothing, so I don't.