I played Pine Barrens numerous times. It was a solid DS 7 "An excellent course, worth checking out if you get anywhere within 100 miles. You can expect soundly designed, interesting holes and a pretty setting, if not necessarily anything unique to the world of golf" (note, I left out "good course conditioning", as that was no longer the case the last few years)
A DS 8 is a course that is one of the very best in the region and worth a special trip to see.
In most cases I don't think it's worth the cost and effort to try to turn a DS 7 into an 8 (or higher). However, in the case of WW, the place wasn't ever a business success, notwithstanding the quality of the courses. The chances that a mere restoration would make the place a success was made even more unlikely given its proximity to the relatively recent addition of Streamsong. In acquiring the facility Cabot likely felt the need to to have a place that is at least a DS 8... worth a special trip to see. So, in this case I can understand why they decided not to just retore PB.
Perhaps the question should be broadened to be "Under what circumstances, if ever, is it justified to tear up and re-do a DS 7 rather than just restoring it?"