Several reasons to stay in bed

Lying down saves energy compared to standing up

In bed it is OK to sleep and when you are asleep you cannot easily do anything wrong and get into trouble

Bed has no distractions and is the best place to do your thinking

There is a perfectly good tv in the bedroom

Any exercise you can only do standing up is too much exercise

Bed keeps you warm and in the winter it is cold everywhere else as well as dark and if it is dark you might as well go to sleep anyway

Eating in bed is fine - the Romans ate lying down and they did alright for themselves

Please feel free to add to the list but nothing rude :¬)