SleepNaked.org is a small, but persuading, campaign about why people should sleep naked.
Not only is sleeping naked more comfortable, but it’s good for your health too. Increasing your level of comfort makes it easier for you to relax and sleep…
If you sleep with a partner, being naked heightens the level of intimacy between you, and you are likely to have sex more often. You may also feel closer to your partner as a result of sleeping naked with them
I guess one can also argue if people sleep naked less pajamas will be bought thereby saving the environment a little.