I've never heard this mentioned anywhere, either canon or non-canon, but in my mind the chairs are ergonomic, which subtlely shift position to prevent the user from cramping up when one's sitting there for a long time.
Otherwise, let's face it. THe basic design of the chair hasn't really changed much in the past few thousand years.
Otherwise, let's face it. THe basic design of the chair hasn't really changed much in the past few thousand years.