We have traditional cable TV, where there are standard def channels on, say, channels 2-99 and then identical HD channels from 702-799, and my wife constantly lands in the SD channels by accident and doesn’t notice the difference. I have switched back and forth between the same show on SD and then HD to show her the huge difference and she just shrugs and legitimately doesn’t see it or care.
I did the A/B test between an OTA broadcast and the cable channel to show people just how poor the cable compression really is. The majority of people could see the difference, but like you mention there's always at least one person claiming to not see it. These are definitely not someone to hire as a QC/QA team member!
