Why do some people like to sleep with the lights on, and some people like to sleep with the lights off?
A lot depends on the environment that the individual is exposed to. In "nature", I presume humans habituated to hot weather during the day, or a warm fire during the day, the the evenings cooling off, as well as the fires dying down at night. Yet, today many of us are quite removed from such an environment.
Some people keep their thermostat more or less constant year-around. Others let it go up in the summer and down in the winter, as well as using a programmable thermostat that will allow the house to cool down at night, and then turn the heater back on in the morning.
A good pile of covers is always nice in the winter!
At least when driving, some people believe a hot car can make a driver drowsy. I wonder if the same would be true at night, or at least crawling under a warm pile of covers. However, I believe that allowing the night time temperature to fluctuate may help a person habituate to changes in ambient temperatures during the day.
I must admit that I have found 100°F temperature at night can be most uncomfortable.