I agree with @quoth.
Just because 
CSS allows way more
features , becaue. it was set for WEB pages.
An e-book only uses a small subset. Even then, the 'we know better' folk that outfitted you device, chose to ignore, or took the code easy way out (User adjustable WITH Publishers settings being Algebraic)
(and Posters, please verify your
general comments on coding are
generally Industry supported on mainstream e-readers
)