When you come out for a job on an old house, with perhaps some "interesting" plumbing, what would be useful? Schematics of the plumbing in the house? Videos of previous problems in previous jobs and the solutions? Records of who did the work?
Presumably if you did the work, you'll remember. But the younger plumbers seem to come and go from companies here, and the memory seems to disappear with them. Plus other things happen, too.
Seems like with the newer technologies, it would be easy to pass on these kinds of memories to the next homeowner.