I spend a lot of time awake in bed

either sitting propped up in bed reading or internet

or lying on my stomach in bed reading or internet

and flat sheets are perfect for that layer that needs to go between

the loose electric heated throw rug (which is great in winter, or for muscle aches/pains)

and my skin

1. so I don't have to wash the throw rug

2. so the synthetic fibres of the throw rug don't annoy my skin (which can't cope with anything except cotton/bamboo directly touching it)