One big annoyance I experienced growing up was whenever my parents forced me to say "thank you" in front of other people. It was bad enough that they teased words out of me with no care for what I actually felt, but to make me say it in front of another person angered me to no end. I'd think "now that you told me to do it, they'll think I won't really mean it! Now there's no point in saying it!" But I had no choice, so, humiliated, I said the words through gritted teeth.
Back then, I understood my annoyance intuitively. Now that I have the words and awareness for it I can say that the reason I was so annoyed was that I wanted to be true to myself. Not only did my parents disrespect my need for being genuine, I was also being robbed of the experience of the feeling behind the words. That's because I was made to focus more on empty words rather than actual appreciation.
Don't get me wrong, I am not against saying pleasantries like please and thank you. I actually do say them, but only when those words reflect my true feelings. What I am against is being coerced to say those words. I simply don't think the feeling of appreciation can be forced onto another person. In fact, this coercion often has the opposite effect. It may create people who will rarely feel appreciative, even if they do end up adopting the words that indicate it.
I think the best way to cultivate appreciative, kind and empathetic kids is to model the virtues yourself. We need to teach them that these feelings come from within and stop making them say "thank you" just because someone else told them to. In order to do that they need to be given the space to feel it.