Why are doctors reluctant to prescribe armour or any ndt? it seems that those who do use it feel tremendously better

Different doctors: have different reasons. In general, however, it is harder to titrate the dose. Since it is simply ground up pig thyroid, there is no guarantee how much hormone you will get with each pill (there is variability). Synthroid or levothyroxine is also biochemically identical to human thyroid hormone, pig hormone is not. Patients probably feel better due to the T4/T3 combo.