This has probably come up before but do you think it is taught or necessary to look over your shoulder to check blindspot when changing lanes on the motorway?
I just need to add an edit. I’m specifically referring to looking over your shoulder on a motorway. Checking mirrors and blindspot is not under question
It sounds like you are describing the Car Talk method.
https://www.cartalk.com/sites/default/files/features/mirrors/CarTalkMirrors.pdf
I used to do that too. Then I started parking by backing in, frequently (a dozen or more times per day), and found that being able to see the rear corners of my vehicle in the mirrors was infinitely more useful.