The main reason I will give to answer your question is: No-till came around in the very late 60s early 70s. So that makes most of us that actually plowed for everything very near 70 or above. I myself always enjoyed plowing and as our farm never had BIG POWERFUL tractors, I learned real quick (from my elders) that small adjustments made big differences in ho easy a plow would pull. My grandfather used horses to farm until sometime after WWII. It was probably sometime in the 50s before  he could buy even a used tractor. I remember when I was 11 or 12 and my grandparents came to the field to pick me up where I was plowing ( thought I'd been doing a good job as I'd not touched any adjustments) and my grandfather walk over and moved the furrow lever a click and said make another round. The tractor quit lugging so hard. When I asked him to explain what he did, he said the plow was not level. 

  I see in most of the videos, the plows are nosed in and leaning left. Most likely due to worn parts and lack of knowledge, but they are rooting around like a bunch of hogs as Grandad would say. 

  I've attended many "Plow Days" where that is the case. Very few place actually have individual areas for each person. Following a poor job, results in a poor job. 

  The last on I took a tractor and plow to many had shins worn the to frog and a few were trying to plow with broken shares. After a couple rounds I could bear to watch the hogs so I loaded up.

 On our farm we NEVER NoTilled and plowed everything and payed attention to the lay of the land on how the rows ran instead of just using the longest fenceline.