10 years ago 3.73 and 4.10 was used on typical 3/4 and 1 ton diesels. Transmissions used 4-5 speeds with the highest ratio about 0.70:1. Torque was about 500lb-ft.
Today, 3.31-3.55 are common and GM still uses 3.73. Transmissions have 6 gears with the highest ratio as low as 0.63:1. Engine torque is now 750-850 ft-lb.
A 2015 Ram diesel with 3.42 and Aisin trans has 16% more torque in top gear than a 10 year old Ram diesel with 4.10.
Why lower gearing today? More power available and compromise on using some of the power/gearing to save fuel when not loaded. All this to compensate for the extra diesel emissions required in the last 10 years.