The trucks seem to get it the worst. I think it has a lot to do with the construction and the shape of the bodies creates a lot of places for dirt, salt and moisture to get trapped versus a car or SUV. On top of the fact that they are just commonly used for work.
Fluid Film (or similar) every year or every other year is the best solution I’ve found.
In addition to this, it also seems that the higher ground clearance most trucks have creates greater air turbulence which scoops up more material off the road to be deposited on the undercarriage.