We recently stayed at a hotel that has a pair of toilet roll spindles in each bathroom. I've seen this arrangement in other places. The idea, as I'm sure you know, is that you keep using one roll until it's empty, and then housekeeping has plenty of time to replace that roll while you start on the other one.
But the toilet paper rolls in our bathroom were arranged to solve an entirely different problem. One roll dispensed paper from the top; the other dispensed from the bottom. Many people feel rather passionately that one of these arrangements is the only way to go. Well, whichever you prefer: we had that one.