[CentOS] Kernel building

I have not even decided if I want to undertake a kernel build, but for 
the sake of discussion, if everything happens to be in the stock kernel, 
why, other than file bloat, would you want to build a custom kernel?  In 
FreeBSD, you can remove all those devices and drivers that are not 
needed, and, depending on how much stuff you add or delete, can make a 
decent size reduction in the kernel itself.  I'm not smart enough to 
know if there is a performance trade-off with a whole bunch of unneeded 
modules or drivers in the kernel, but perhaps common sense tells me that 
there must be some kind of performance hit otherwise.  Kernel building 
in Linux is very much different from the BSD camps, and I'll admit I'm 
not sure I understand enough about the Linux build process to undertake it.

Comments appreciated......

-- 
Snowman