In the setup package, the csh.cshrc has been replaced by a
csh.login configuration file. However, the latter is only
read for a login shell, not by a shell started in an xterm,
for example. Since a login shell also reads csh.cshrc, the
basic configuration should be in csh.cshrc, and only
login-specific stuff should go in csh.login.

Reference : tcsh(1) man page

This is pretty obvious to anyone familiar with unix shells.