American Airlines way back had "more room" seats which were only slightly more expensive. I loved it and became loyal. But then they stopped. I guess not a lot of people wanted to pay the few bucks.
Most airlines also build free or discounted access to those seats into their frequent-flyer perks, though Delta has recently begun cutting back hard on that and treating it as a possible-but-not-guaranteed after-booking "upgrade" even for their top-tier customers.