Why don't most car makers offer the same rear axle gear ratio options for the auto vs the manual trans?

I own a 2012 Mustang V6 auto. It's a great car, but the stock 2.73:1 gears are too high and they're more geared toward gas mileage and freeway driving vs a balance of economy and performance. I could have ordered 3.31:1 gears, as a stand alone option, but I did not want to order the car and wait for weeks for it to be shipped in, just for a the gear option.

Ford offered the GT Mustang with either the stock 3.15 or the optional 3.55 or 3.73 gears. As far as I know, there were no gear options for GT autos, only for manuals and as I stated, the V6 could be optioned with 3.31 gears, with either trans.

I did some research and it seems that many, if not most car manufacturers either don't offer gear option for the auto trans at all or they offer only slightly lower gears. But, for the manual trans, not only do they come standard with lower gears, but some car makers offer even lower gear options for their manual transmissions

So, my question is this: Why are such low gears offered as options on most manual cars, but not for the autos? Obviously, it can't be because the manufacturers assume auto buyers are less concerned with performance. Otherwise why would Dodge even offer 470HP SRT Charger and Challengers with auto transmissions? And why would Chevy offer the auto trans on the SS and ZL1 Camaros? And why wouldn't they offer performance gears on these car that are very obviously performance cars, regardless of the which trans they have? The same can be said about the GT Mustang There has to be a technical/mechanical explanation vs a marketing reason.