I have a friend who just bout a new Winnebago Class C. He said in order to put the slide out the ignition has to be on or the engine has to be running? I did not question it because I have never had...
If your slides work off the chassis electrical system, when the engine is running, the system voltage usually jumps to about +-13.2 to +-13.8 volts (possibly higher) instead of the battery rest voltage which is usually about +-12.8 assuming a fully charged battery.
The slightly increased system voltage helps the slide motors with a little extra voltage "push" which makes it/them work better. (just the opposite of a drained battery)