Yeah its like that at my work to, people sign and are told they have to do every shift, nights, mornings, evenings weekends.
But in the end only a couple of us are screwed that way , and we are used as fill up on the schedule and my shifts have been all over the place.
Doing a nightshift end at 06.30 and better not sleep to much because you have to be back at 06.30 the next morning. And the people that get the easy schedule are also the lazy idiots that hardly do anything , or when they do leave such a mess for me to clean up. Man I hope they never give me the job of planning the schedule, those idiots I would play around with so they would just quit.