UP and BNSF-A grade too steep?

[CSSHEGEWISCH]

I will assume that the grades in question are Donner, Cajon, Tehachapi and Raton passes. The first three grades would require major line relocations to reduce the grade and would probably cost more money than anyone would be willing to lend. For the most part, Raton Pass has been bypassed and traffic over that grade consists of little more than the "Southwest Chief" and a handful of coal trains.

[Junctionfan]

Why does UP and BNSF still have thease grades that require helper service when they often have motive power shortages. CP and CN does not use helper service unless off course it is long and heavy unit trains but as far as I know the helpers originally came with the train. Why doesn't UP and BNSF try to reduce their grades?