system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are people more comfortable sleeping with a blanket over them even in warm climates?
gpt
There's a couple reasons. 

One reason that has already been stated is that it's a psychological thing. Maybe in school you studied psychology and learned about Maslow's hierarchy of needs. Basically this is a principle that states that in order to achieve higher levels of comfort such as self-content, one must have the most basic levels of comfort such as shelter and security. A blanket provides a type of security that makes it easier for your animal brain to calm down at night and fall asleep. 

The second reason is air movement. Even in a 75° room, if there is a ceiling fan going and you are laying there with your shirt off, you will feel chilly. Throwing a blanket on gives you your own comfy little microclimate.