Why no 3rd rail on Hudson track 1?

I see there are a couple of gaps, several miles long, in the third rail on track 1 (east of Tarrytown, and thru Ossining). Looking at the ties, no sign it ever had third rail. But surely it did? When did it come out, and why?

MNCR actualy wanted to remove track 1 in 1984 to cut cost, but CR and AMtk went to court due to delays already on Hudson line.
so the track had to stay, but MNCR took down the third rail as cost cutting measure. from CP12 to CP19 the third rail was replaced to compensate for track outages for construction of new platforms

Correct me if I'm wrong, but roughly 50% or more of trains running to and past Croton Harmon are pulled by a diesel locomotive or one with diesel capabilities. So to cut costs like DutchRailnut said, MNCR removed some third rail.

Would the cost savings be from property taxes/maintenance or from charging the 3rd rail? I'd assume it had to be one of the first ones not the electricity as I can't imagine that much energy is used when the 3rd rail is idle, and even if that was the case, they could have just shut it down.

maintaining third rail for 30 or so miles runs in the millions per year.