That is true. But I think it very likely that my generation is to blame.
Some two decades past a friend was providing most of the child minding for her toddler grandson. I was visiting one afternoon, tea & biscuits. The grandson indicated his desire for a biscuit – the plate was by my side. Say please, I automatically instructed – only to get my head bitten off by my friend. Don’t say that! He can have a biscuit if he wants one, he’s only little, he doesn’t have to say please.
Well, I probably had presumed too much, but my memory of childhood is that grown ups always told you to say please if you wanted something - & not just parents, relatives, neighbours or teachers but complete strangers too; everybody had a duty to teach good manners to the young.
Strangely though I think it was only your mother or others close to you who instructed you to say thank you. I particularly used to dread – though I cannot work out why - the moment of leaving a children’s party when mother instructed you to say good bye to your hostess & Thank you for having me.
It is about ten years ago now though since I started to notice the real advantage of saying Please & Thank You to those who are now in their teens or twenties. It was in some shop that I asked Please may I have X – I don’t think I ever do it more abruptly - & the girl serving almost went Ah, how sweet! Of course you can, she said. It still happens quite often.
It even works on the kind of teenage male old ladies are supposed to find frightening or alarming; if they are blocking your way just say Please can I get past? & they move; I don’t even mind if they say Of course you can, love, though I bristled at the hoody who called me darling.
On younger boys – aged about 8 to 12 – the affect is comically & sweetly galvanising. I have twice had the experience of having to ask boys to move so I can continue to negotiate stairs on the side which has the hand rail. The first lot were engaged in a play fight but they immediately jumped to the other side of the staircase & flattened themselves against the wall, saying Sorry! And just last week when I had to go down a steep stone stair case in town because the usual path is closed for repair I came across two boys sitting there, up to some kind of mischief judging by their demeanour. But as soon as I asked one to move so that I could continue to hold on to the rail, he too jumped up with apology & shot to the other side – perhaps just grateful not to be ticked off or reported for whatever it was they were up to.
Mind you I never use, & would not dream of instructing a child, to stick to the other nicety which was drummed in to us.
If you asked to be allowed to do something: Can I get down from the table now, please? the answer was Well you can, but you may not. You really were not granted your wish until you used the precisely correct word.
PS It is disappointing to learn from the OED that The expression [P's & Q's] is unlikely to be a shortening of pleases and thank yous, since this is apparently not attested independently as a phrase before the 20th cent.