Exponents in <number>

According to CSS 3 Values and Units, numbers can't be of the form  
1.0e20.

http://www.w3.org/TR/css3-values/#numbers

"A <number> can either be an <integer>, or it can be zero or more  
digits followed by a dot (.) followed by one or more digits."

Was there a reason for not allowing this?

Would it be possible to change the syntax to allow the format? (I  
assume this would be classified as a significant change)

Dean