Warrior Ancient and Medieval Rules

In the old WRG 7th you could mount the Druzhina onto horses

Is there any reason why you cannot in Warrior list ?

or is it an error
As you can mount the Generals Element I would have thought the
Druzhina would be allowed at least one element to complement the
CinC ??!?!??! Also theres no way the Druzhina being a better class
of troops are going to walk and the Lowly spearmen can ride ;)

Just a thought

Mike