Red_Lives wrote:And they are twin-linked at that
Not entirely true.
There's a heavy weapons version that the standard Kriegers have which is twin-linked and mounted on a gun carriage.
Then there's the single, man-portable version that the
DKOK Grenadiers have.
As for why we don't see them, the assumption is because Heavy Stubbers are considered "antiques" by the Imperium at large. Remember that the Gaunt's Ghosts series, where they were popular, is set some 300-400 years(at least) prior to the current timeframe.