Because lots of people are fine with spending $10k extra to go faster, and have owned 2 or 3 trucks at the most with a couple hundred thousand "mostly trouble free" miles between the lot of them.
Use whatever math you like to justify it to your wife. I'm telling you, best case financially is a wash. Worst case is a $20k engine replacement. You can replace an entire gas engine for what a fuel system failure on a diesel costs. That's a hell of a risk to take if you aren't towing real heavy real often.
Your logic just doesn’t fly . I’ve been in this towing game for a good 50 years , you couldn’t give me a gas powered truck . I’ve towed many many miles with gas , and some of it not a pleasant experience, screaming hi rpm’s, white knuckle coming off steep grades , under powered etc etc .
I will say I certainly wouldn’t own a diesel powered truck for daily use , doesn’t make sense . I tow heavy ,my Ram gets used for what it’s intended for. If it gets 5k or 20k a year , it gets worked .
There’s no monetary, or justification in my mind whatsoever. As said I don’t want to listen to a screaming V8 climbing a mountain grade , nor a white knuckled butt puckered experience coming off a long 10-15 mile grade . Every time I come off these mountain grades that I do annually I get a smile on my face with this Cummins . One especially in Idaho , around a 10 mile grade , it’s only 60 mph , no big curves . I set the cruise for 50 , she runs 55 , and I don’t touch a thing until the bottom. Feels no different than running on a flat road . Relaxed drive going up , and down that grade , that six banger Cummins just chugs up that grade without a lot of effort.
I can guarantee you my wife enjoys the towing ability of a diesel, I never had to sell her on anything. I decided to go diesel 26 years ago , my truck , my decision. Her car her decision on what see wants . That’s how it works with us . Been married for 54 years to her , and we have never bought a single thing we couldn’t afford , or tried to justify why we were buying it . It’s what we want , we can afford it , we buy it . Pretty simple process for us . No cost analysis, no worrying about what COULD happen. We don’t live that way .