Some trucks, and some jobs for the truck, in some locations, hauling lots of fuel makes sense. Back when I was running 427 GMC, and working it hard, a lot of days a 50 gallon saddle on each side would not last all day. And often that 200 gallon tank on the F 750 was worthwhile. But now, for what I use the pickup for a extra gas tank even for free would not be worth the cost.
If somebody only hears cheers for them they are less likely to really think about their need for the tank.