Manufacturers design their chassis with a certain amount of sway built in. It's there to let you know when things are getting a little hairy out there. If you intentionally reduce that safety margin by stiffening your suspension, well, . . . . bad things can happen pretty fast. If you are seeing 80,000 lb. 18 wheel trucks blown over, you might want take that as a hint to get off the road.
Of course worn shocks and suspension/steering parts should be replaced as soon as possible. Upgrading within reason makes sense.
Chum lee