In three words; Duty cycle and heat.
Turbo's put out a lot of heat any they make the engine put out a lot of heat. At 14 pounds of boost they are doubling the engine size. So if you have a 6 liter N/A engine you now have a 12 liter engine and it's hard to keep a 12 liter engine cool running full tilt pulling a hill with a heavy load.
Then there is the fuel economy issue. You now have a 12 liter engine using 12 liters worth of fuel. A 12 liter engine can use a LOT of fuel. My 9 liter engine can use about a gallon of fuel/ 1/4 mile. Or 4 gallons/ mile. (no, not a typo)
~ Too many freaks & not enough circuses ~
"Life is not tried ~ it is merely survived ~ if you're standing
outside the fire"
"The best way to get a bad law repealed is to enforce it strictly."- Abraham Lincoln