Or is only mattresses, because pillows could be used as a weapon?
Yes
Yes. Pretty thin ones.
My wife worked in a prison for a bit.
It depends on what area, and how much they budget for “luxuries”.
I had a vinyl mattress and no pillow. It was just jail overnight once, and another time for a weekend.
Mattress like a blue gym mat. No pillow. Bartlett (suburb of Memphis) municipal jail
If they don’t have pillows how could they have pillow fights et al.