Should not furniture conform to the body and not the other way around?
There is evidence to indicate the typical chair supports the body in an unnatural position and forces the back to bend in ways it is not designed for.
These stools are an alternative for those who have an uneasy relationship with conventional seating. A forward sloping seat permits the hip joint to be more open, allows the back muscles to strengthen and be more active, and encourages better posture.
Don't take my word for it. Ask your back care provider. Read 'THE CHAIR' by Galen Cranz.