My brother was a DJ in the 90s and this was the case for them. They had a pretty rigid schedule that required certain things at certain times and I don’t think even the station owner could do much to deviate from it. If memory serves, it was the FCC, some of their music and content providers, and state/local regs all requiring various things be done daily, hourly, weekly, etc.
Obviously things could be very different now, and I would guess there are some slight regional differences.