In universe answer? Most forces on offensive operations of any significant duration likely need to bring along additional DropShips to deal with support staff. This does pose some interesting questions, considering the paucity of DropShips and naval assets in general. Monarchs are great choices for personnel transport, considering they are one of the very few (if not the only) DropShip configured for actual passenger transport. In theory, any ship with a decent sized cargo bay can convert it into passenger transport, but I'm not exactly sure how simple that is. (They really, really needed to just create Omnibays, at least for cargo/passengers, especially considering how much of a canon DropShip is empty space.)
Out of universe answer? It only gets more complicated. The DropShip bays have room for the technician and combat personnel only, not the full technical team of one tech plus six astechs. StratOps also seems to point towards the fact that many forces simply higher astechs locally (which seems like a potentially massive security leak for forces conquering a planet). This is further complicated by the fact that it seems Total Warfare wanted to avoid retconning exactly what the various bays carry, even while they expanded what technical teams were in StratOps. It's not a design decision I thought was particularly wise.
With the return of smaller raids in the current material, versus larger planetary conquests, I'm hoping that we see the ranks of DropShips filled out. Unfortunately, knowing the reality that the CGL and freelancer personnel are faced with in terms of creating accurate recordsheets and TROs in anything resembling a timely fashion for any non-Mech units (due to a whole lot of issues, not the least of which is lack of up to date software)...I'm not holding onto that hope too tightly.