the logic was "why should I say please when I buy something, I'm paying for it. Why should I say thank you when they give me change, it's my money."
This is interesting. I used to think like this. Why are customers thanking cashiers when they give them change? It's their money, they paid for the goods and the money they are getting back is their money, so the cashier isn't doing them any favours by giving them their money back. I got over that now though. It's just politeness, so why not say thank you? The cashier can say thank you too, when receiving the money for the goods, even though in many cases [unless she owns the store] this money doesn't go to her, but to the store she works at. It just makes the entire transaction more pleasant though.
Having said that I do occasionally get frustrated with myself for giving somebody an undeserved 'thank you', like when I'm in my car and I think a car is letting me through, so I thank them, then I realise they are actually just parked up on the side of the road. It doesn't matter though. So they got an underserved thanks, big deal. I have sometimes given people a very underserved 'sorry' though. It's usually in a crowded place, when somebody barges past me. Then I think, ah man, they frigging barged in to me, why did I just apologise? I was standing there, it isn't my fault.
By the way, speaking of the 1st incident with the car, I was recently reading a humorous but semi serious article about road etiquette, and it said that the driver who let's another through, should return the 'thank you' wave after being thanked. So say you move to the side of the road and stop, in order to let a car from the other side past because the road is too narrow for both of you to get through at the same time, when they raise their hand to thank you as they go through, you should raise it back to acknowledge their thanks. The explanation was that it isn't really a return thank you, but more of an acknowledgement of their thanks. Apparently if you don't do it, the other driver might think you begrudgingly let them through and weren't happy doing it. It seems a bit over the top and I never used to give the acknowledging return wave, but I've done it a few times now. I can't imagine a Polish person would be keen on all this though, most drivers are maniacs. Anyone heard of this 'road etiquette?'
Oh, the reminds me of something else that annoyed me in Poland. Why the heck can cars run a red light, while if a person walks to the other side of the road when they have a red, they could be fined? It seems cars have more rights than pedestrians in Poland.