In aviation some rebuilt engines cost more than new entire tractors. In aviation we use CHT heaters or individual cylinder band heaters along with oil sump heaters. This is because most aviation engines are air cooled so no block plugs or radiator hoses..anyway, the reason for heating is only slightly to make it start like it's June outside and put minimal strain on the battery which in aviation is pretty compact and costs twice as much but rather it is to heat the block, cylinders, rings, pistons and oil, crank and parts that upon startup over 70% wear occurs. The oil begins to flow immediately and helps protect your engine. Some aircraft even have pre-oilers to circulate the oil before startup to further minimize wear.
Preheat is, at least in aviation, for your engines protection.
I can see diesel tractors need help starting in sub zero temps and it only makes sense that the use of a block heater should provide more engine protection than any other method. At least quicker cyliners to temp...