How do some people come up with the idea that a block heater is a conspiracy against them by the manufacture or dealer ? Engine wear is the highest when cylinder walls are cold with coolant temps below 180F. The same person that is all worried about engine wear and changes the oil and filter at reduced hours. Is all too often the same person who doesn't use a block heater but hammers an engine to life in the winter with ether , jumper cables or long duration use of glowplugs/intake grid heaters.
Your ears will tell you that a stone cold diesel rattling and hammering is less desirable than a preheated diesel that starts on the first turn and operates smooth.
Less wear on the starter, battery and alternator.
Windshield defroster operates sooner without wasting fuel and causing increased engine while idling waiting for cab heat.
We plug the gas vehicles in, even though they start without preheating just to have near instant heat from the windshield defroster.
You must remember though that everyone doesn't live on Lake Huron or even experience winters close to what your typical winter would be. I use my tractor very little through the winter months and too be totally honest, It's not often that it's below 20*F around here so when it is there's not much that can't wait for better weather. So, if mine starts the few times I need it in cold weather without a block heater then I'm happy without one.