Yard Switcher Locomotives - Model Railroader Magazine

It seems railroads haven't been buying new switchers in any quantity for a long time. Those SW-1200 / 1500 EMD switchers that are still around go back to the 1960's, and the MP-15 (technically a road switcher - switcher body on road-engine trucks) dates from the 1970's.

Part of it I'm sure is frugality - using what you already have. Why buy new switchers when an old GP-35 or whatever you have will do just as well? Interestingly, railroads are kinda going full circle...100+ years back, railroads were taking the leading wheels off of old 2-6-0 or 2-8-0 engines to convert them to six or eight wheel switchers.

I wonder too if power needs factor into it? Cars are a lot bigger than 50 years ago, more weight. If one 1000-1200 HP switcher can't do the job, why use two 1000 HP switchers, when one 2000 HP road switcher can do the job?