why do new kernels insist on uninstalling old?

[sean]

Using yum I have kernels install only:

installonlypkgs=kernel

yet with the new 2.6.19 kernels, yum insist on uninstalling 
the old kernels.

Removing:
  kernel                  x86_64     2.6.19-1.2885.fc7 
installed          60 M

Why?

Can I fix this?

I'd really like to keep my old kernels, until I'm satisfied 
the new ones work.

sean