Asside from the safety concerns, one other concern from a manufacturers stand point is they would be condoning abuse. Thereby would run a great risk of paying for some very expensive warrantly claims for damages to the mast rollers, the upright channels, mast to axle mounts, etc. These components & others all take an impact pounding when they are used as "bulldozers" that they are not designed to do. Don't think they wish to do that in a saturated - competitve market place.
On the lighter side, if they allowed it after a major redesign the manufacturer would need to rename them from LIFT trucks to NUDGERS. Bulldozer are designed to "bull doze" & make ugly lift trucks.
End users need to Pony Up and buy the right equipment for their pallet moving or revise their material handling methods. Most bulldozing I've seen is when the customer has a forklift that is too small for the job or they are very lax in their operator saftey training, company procedures/policies & periodic review of operator skills.