Actually, I suspect it was more that nobody builds a tractor with manual steering anymore. (The package trucks have power steering now for the same reason.)
They will build a truck anyway you want. Hell, we lease from Penske, and we can have anything we want to order right down to the color of the truck. Now if you take it off the lot, that's a different story.
I've been doing this a long time, and I know how companies try to cut the extras to save money. Years ago larger companies didn't even provide air-ride. But the medical claims from drivers (which were many of them) for back problems made it more expensive in the long run, so they all went to air-ride. I drove a truck years ago that didn't have it, and those things could shake the fillings out of your mouth. I couldn't drive over 50 mph, and it shook so bad you couldn't even select a preset radio station on your radio.
The extras did get cheaper to buy as years went on. But companies found it more advantageous to get the extras. Air conditioning is another one. Drivers fell asleep more often without AC when it was hot and muggy. This is not to mention how terrible their drivers looked when they went to a customer being all sweaty and looking like you just got out of a war zone. Many times the drivers took breaks in the company cafeteria at their stops, or somewhere that had AC just so they could cool off for a while, and that really slowed things down. Now just about everybody has AC.