They were valued for both having a lot of background knowledge in their area, and having an ability for judgment about detailed problems that could only be called "wisdom."
Management kept them around like wise elders because once or twice a week there'd be some task that others could do, but not as well or as thoroughly (use of judgment, again) as these people. Thus problems got transferred to them.
The counterpart to these people are Suzannes, named after the first one I met. You can have an office full of highly technical people, but Suzanne -- who usually doesn't get paid much, and is some kind of administrative staff -- is the person everyone asks questions of nearly constantly because she knows all the ins and outs of the business. Every office has a Suzanne, and often the place won't function if he or she is out sick for a day.