Well, you should not seat for long periods of time.

If you do you train your body, the same way that if you look just with one eye you modify the eye you don't use, you modify your spine if you seat or use heels for long periods of time.

A good chiropractic professional could read your body in an amazing way.

Once you have modified your body by use, being "comfortable" is not the same as "healthy". Smoking is comfortable for a smoker, taking drugs is comfortable for a drug addict and covering one eye is more comfortable than using it once you have used only the other for a long time.