These players don’t use auctioneer scans because they…
- …Know their markets so well that they can search for mats and review prices manually a lot faster than it takes to run a scan. Depending on the number of markets this could happen pretty quickly for most auctioneers.
- …Prefer to flip a few big name items while allowing an untold number of smaller flips to go untouched.
- …Use addons like QA3 which are doing the posting and not auctioneer, so why keep a scan going to maintain the database when it’s not the one posting?
Well, and I apologize for talking in the third person but it’s just too much fun, the simple fact is that like anything in life you need to start somewhere before you can take off and become an expert. Auctioneer does exactly what these ah players are doing in their heads: tracking prices, cycles and related values. Once you see the numbers enough you can do this as well and save time, but until then you’re going to have to rely on a machine to take care of it for you. If you really hate addons well you could theoretically keep track of all the data on excel spreadsheets or even on pen and paper but it's going to slow your growth as an auctioneer.
It's also worth noting that you should still have auctioneer even if you don't use the scanning, various searches and snatch features. The PCT column and other sorting mechanisms alone are worth the addon's weight in gold.
Now if you’re a player who enjoys the “fishing-like” nature of running scans and putting out bids/buyouts on random items then using auctioneering is a time saver. If you’re into profession crafting and material management for more reliable income then you can probably give up on auctioneer once you’ve learned the markets well enough.
Image taken from Starcraft 2 "scanner sweep."