Because they were just used to designing gear trains, not gear trains for open-loop motion control?
AFAIK these motors are made specifically to steer airflow in air conditioning systems, which is the
reason they are so cheap and why exact gear ratios aren't part of the original specifications I suspect.
4096 steps sounds great but the gear train backlash means a standard stepper motor with microstepping
controller probably outperforms this motor - except in price!