So!
In JSL's post at towards the bottom of page 12
We check boarding passes because, in the UK at least, it is a directive for UK based airlines. It's not our choice to make.
So that settles the discrepancy with other European Carriers.
If I'm lucky I fly maybe 4 times a year but can remember: -
Check-in show appropriate ID get boarding card
Show boarding card at security
If I buy anything in duty free - show boarding card
At the gate - show appropriate ID and boarding card
At the aircraft - show boarding card
Keep boarding card in case it is needed elsewhere.
Now somehow I don't find that difficult to remember, I appreciate that very infrequent flyers may not know, but really fail to see how an experience traveller can't remember these simple steps.
The whys and wherefores are a different matter, I wonder how many of the grumps rather than post on here have actually taken the trouble to take the matter up with the appropriate authorities, come on own up if you have.
Next folks will be complaining about showing their passports at immigration.