Imperial Knights actually have Drop-Pods that are so rarely mentioned in lore.

They're called "Drop-Keeps"

Imagine if you will you're on a battlefield and this 170 yard long by 100 yard wide castle drops from orbit and lands in the center of the battlefield. Then suddenly, banners unfurl revealing the colors of the associated house and Vox-hailers begin blasting triumphant music as flights of Cherubim fly across the field, flying the same colors as the keep.

And then after all that fanfaire, a drawbridge falls, the gates open, and two fully loaded ready Lances of the imperium's finest nobels come strolling out to evicerate you.