That practice used to be common because stations had to be attended 24/7 until 1995. Plus, automation wasn’t as reliable as it is now. As making money on overnights, even for successful stations, was difficult, many just signed off. There were ways to outsource your attendant prior to '95, and, at some point, your engineer being on call all night while sleeping qualified as attended so long as he was in a fixed location with a landline phone. Directional AM stations, however, even still have to be checked at least every three hours, though, today, a computer dialing in is now acceptable.