An operator might be able to answer this question with conviction:

If you regularly look after a pin, keep it clean and protected, and fix issues as soon as they crop up, is this less work in the long run than neglecting the machines like many ops do? Is there any economical sense (time or money) to ops neglecting their pins? I can't understand why such horrible neglect is the norm.

That answers the question I guess. I would have thought that neglecting your pins is the best way to reduce your ROI when selling up the pin later on, and lose your high-end customer base (repeat players). If one op doesn't take care of his pins and a competing op does, you can be sure that the money will go to the op that keeps his pins in good playing condition.

In my city there is only one operator. A few years ago his last remaining competitor got out of the game. Since then all the pins in the city have gone down hill fast and they are all far below average and I consider them unplayable. This is obviously still working for him because people have nowhere else to go. I so desperately want to save his pins from destruction, but I have to watch them deteriorate and reinforce the public perception that pinball has faded into obscurity.