Actually, not really an insightful post.
AA tried that a failed miserably.
That's a common misconception among those who haven't studied the numbers and the history surrounding AA's MRTC initiative.
MRTC didn't "fail," but AA did abandon it in the difficult years following the September 11 attacks.
MRTC was announced in early 2000; the domestic fleet featured it by the end of summer, 2000. The international fleet was converted by early 2001. A few short months later, AA's revenue plummeted (along with revenue at all other airlines). Nevertheless, AA's yield bested the UA yield for several years while UA languished in Ch 11.
When AA announced the rollback of MRTC, it claimed that the incremental revenue from reinstalling the seats would be about $150 million each year, at a company with annual revenue of about 140 times that much. The incremental revenue was a drop in the bucket, but the company thought it important enough to slowly cancel MRTC.
Reducing seating in an aircraft and still flying the aircraft means you have to jack up tickets to cover that airplane's operating costs. The only true way to lower costs is to park them or get rid of them.
Nope, you don't have to "jack up" fares on the remaining seats. Attracting an additional expensive fare or two per flight from your competition (which, of course, would increase your average yield) would bring in plenty of money to pay for more seat pitch.
It's true that AA never tried to charge extra for MRTC (as UA finally did). Same at B6, which now tries to charge more for its extra legroom seats (all B6 seats feature more pitch than US, UA or AA). B6 has removed two rows of seats from all of its A320s (essentially, the same thing AA did on all its planes), but the motivation at B6 for the first removed row was to avoid more fines from the FAA for failure to have onboard space for wheelchairs. Dunno why B6 removed the second row, but it had the effect of extending the transcon range of its short-legged 320s.
Before B6 removed the seats, it had turned to small losses instead of profits (just as the legacies were finally beginning to recover from the 2001-induced revenue disaster). Once B6 removed the seats, it slowly returned to profitability. Dunno if there's a causal relationship, but there's certainly a correlation.
UA says that its E+ upcharges bring in substantial revenue, as does B6 with its recent charges for its extra legroom seats. Since some people will pay more for more room, it stands to reason that extra room at every seat will increase the average yield of the flight (since some of the people enjoying the room probably paid more). Fewer seats means higher average fares, no?
Failed miserably? The numbers don't bear out your assertion. Abandoned? Yep, AA abandoned it (prematurely, IMO).