Why can't I ugrade Fedora like Centos?

[Timothy Murphy]

I upgraded from CentOS-5.3 to CentOS-5.4
(and earlier from CentOS-5.2 to CentOS-5.3)
just by running "yum update".

Why can't I upgrade to Fedora-12 like that?
Is it just that the CentOS makers are cleverer...?

-- 
Timothy Murphy  
e-mail: gayleard /at/ eircom.net
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland