c++ implies -fno-builtin -- why?

[Paul Koning]

In digging through the docs I ran across the statement that C++
ignores -fbuiltin and always runs with -fno-builtin.

I was wondering why.  Is there some language law reason for this?  Or
is the issue that it would have to be done differently from the C case
(effectively implementing "mangled" flavors of the function names to
match against) and that hasn't yet been done?  Or some other reason?

      paul