When I ssh into my ubuntu-box running Hardy 8.04, the environment variables in my .bashrc are not set.

If I do a source .bashrc, the variables are properly set, and all is well.

How come .bashrc isn't run at login?

.bashrc is not sourced when you log in using SSH. You need to source it in your .bash_profile like this:

if [ -f ~/.bashrc ]; then
  . ~/.bashrc
fi