[Rd] Byte compilation of packages on CRAN

[Matthew Dowle]

In DESCRIPTION if I set LazyLoad to 'yes' will data.table (for example)
then be byte compiled for users who install the binary package from CRAN
on Windows?
This question is based on reading section 1.2 of this document :
http://www.divms.uiowa.edu/~luke/R/compiler/compiler.pdf
I've searched r-devel and Stack Overflow history and have found
questions and answers relating to R CMD INSTALL and install.packages()
from source, but no answer (as yet) about why binary packages for
Windows appear not to be byte compiled. 
If so, is there any reason why all packages should not set LazyLoad to
'yes'. And if not, could LazyLoad be 'yes' by default?
Thanks,
Matthew