Lack of up-keep?
If you knew SP like I did (worked for them), there's your answer.
Seriously... it's old. Speed lettering began in '91, so that car is at least 25 years old. Then I will bet that, during the various downturns, it was stored somewhere in coastal Texas on an embargoed branchline or another humid location. I recall strings of stored cars on the SP in the Sacramento River delta area about 10 years ago.
