For engine builders like myself and others, the Dyno is a great learning tool WHEN you compare that data with flow bench data, and real world at the track data...to customers the Dyno is a great way to get the engine broke in, check for leaks, fine tune the engine for the air it's breather on that particular day (baseline tuneup) and try a few things that might make more power like lash, timing, etc...saving some time at the drag strip possibly.
I've seen a poorly setup car (with incorrect front end alignment) make a good engine look bad...what do your calculators say about that???? Oh, NOBODY has a poorly setup chassis....LOL!