I recall the reasoning was their shipyard clogging and odd AI matching.
This is because a tug usually costs less than others of it's hull size, often costing comperable to something a hullsize or two less.
When AI selection schemes pick the largest hull that's near your BVP, we ended up seeing them every mission, pretty much.
If the latter is solved, then there's still shipyard production (for the same BVP reasons it's seen so often) to consider.