Going to bed

The other night I was laying in bed and it got me thinking about how illogical going to bed actually is.
I mean think about it, not the actually going to sleep bit, our bodies need to sleep, but the going up to bed part, it just doesn't make much sense.  We spend all day wearing warm clothes in a nice warm room, then we take the warm clothes off and put thin cold ones on, then we go to a cooler room to go to sleep.  Madness! why not sleep in the warm room in the first place? I mean we have hot water bottles and electric blankets to try and get warm in the cold bedroom, as Spock would say  "illogical captain"