^^^^^^i think some of the reasoning with LNG conversions to the big blocks was extended engine life/mileage as well. I dont know how the hybrids hold up under extreme mileage use. Chances are they just flog em before they get as hi as the older LNG V8 conversions.
The way i see it NG was way cheaper 1/2 the price of RUG back in the day but you lose power so a bigger american engine was a good thing and they could just thro cheap used parts at old junkers
They are now using hybrids because it makes business sense I took a ride with a cabbie who told me he expected to keep his Prius for 6 years/600,000 kms