You really believe the trade barely changed? Harold was logging soot levels by hand and noting which brush he used, which tells me he had to know his flues cold because there was no camera to check his work. Now we run a scope up there and see everything on a screen, and honestly a lot of guys skip the feel of the brush on the brick and just trust the picture. That line about the widow says more about Harold than the trade anyway, he knew she couldn't pay and still climbed up there. What he wrote down was a habit we mostly lost, not a tool that stayed the same.

Get why people just buy the whole thing though, one little scratch or burr in that bore and your new seal is toast in a month. You got lucky with yours but a reman unit comes tested with a warranty, so if it fails you just swap it out instead of pulling the thing apart a second time. Plus not everyone has a garage, the tools, or the time, and paying a shop to rebuild costs more in labor than the part ever would.