I can offer some insight, as I was both an amusements manager and wanted a pinball.
Bottom line is, that it is too difficult to maintain pinball machines to the standards that D&B has (had) for their games. They really were top notch when it came to maintenance with mandatory next day delivery for parts, having at least one game completely torn down a week for cleaning and preventative maintenance, polishing all coins in the pushers every monday, etc. I don't seem to see that these days though. Cost cutting, I'm sure. That, and I think they're dropping their target audience age. We had a SP and a RFM, and I PM'ed them every week because I enjoyed it. I think any longer and they would start to look bad, which didn't fit into the regular PM schedule. At that point, I couldn't get parts for either so it was a big deal that they were still allowed on the floor with broken plastics and whatnot.
Nice thing about a CEC, is that their target audience these days is too small to even play pinball. I bet they see a lot less wear and tear than we did.