Customer's spoke with their dollars. Trucks weren't used like they are today. Trucks were fixtures of the farm. It was single cab, bench seat and 8 foot bed for 50 years. Then people started putting their kids in the cab versus in the bed. I grew up as a 'bed kid' I hung out in the bed of the truck everywhere because there wasn't enough room in the front. If I sat in the middle of mom & dad, the extra tall floor shifter would hit me in the leg when dad went to reverse gear in our Chevy. so I'd be in the back with the dogs.
The world changed and people started optioning 4-door models. my dad got a RAM quad cab back in the 90s. the back seat was really small but it was more comfortable and he got a topper on his 6-7 foot bed for hauling stuff around to and from job sites and complaining that 8 foot 2x4s would hang out the back but I was no longer getting rained on or used as a weight to hold down a load of insulation on the way back from the lumber yard.
Safety, standards and trucks as luxury items basically made the American truck the top selling vehicles in USA and Canada. Everyone was buying them and expecting car amenities, comfort and 'hauling' became a one a month ordeal. You need to grab some plaster and paints you can pop off the tonneau cover and take what you need but the other 25 days a month, you'd be hauling the dog and kids and all of their crap with airbags, seat belts and sunroofs and heated seats.
You can still purchase a single cab 8 foot half ton truck and it comes in white and. you wrap it in your contractor company vinyl and you buy 10 of them and their work trucks. These still exist but no American family is buying them.
If you run a focus group, every single RAM customer is going to say they want 4 adults comfortably seated in the car versus an 8 foot bed. Smaller group but still majority want that over a 6.5 foot bed. Americans would rather seat 4 adults of 3 kids in the back than have a foot longer bed.
So if you scour the country for Big Horn / Laramie / Limited trucks for a 6.5 foot bed, you'll find less than 10 of them. a 21 foot long truck won't fit in a garage, won't fit in most parking spaces and won't work if you have to go into the city for any reason. It's a special truck size for people who still need to fill up a bed and need as much space as possible and those people aren't buying Limited trim vehicles.
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I own a 6.5" bed Limited and I fill it up with motorcycles and wish I could close the tailgate with 3 bikes in the back but I can't. I also live in northern New Hampshire. There is never a time when I have an issue parking it ever. I'll pull through parking spaces and hang over 2 feet in another spot but I've never had to navigate a full parking lot before. 80% of my miles are interstate and I don't have a garage.
I'm not most Americans and so I'll have to accept the fact I may have a hard time selling this thing in 10 years because most people aren't going to want a truck this long.
Most Americans now live in cities that's why the Tacoma/Maverick/Ranger sell so damn well even though they're only a few grand cheaper than a base model half ton.