Never went on a management course and never been a manager, I always say please and thankyou. It's polite. Sorry you have a chip on your shoulder about it though.
I think there is no hard rule. Some people say that all the time, some never. Some have a friendly tone and don't need it, but if they add it suddenly it can appear like mentioned. No one said you should stop and I'm pretty sure it won't annoy people if it comes naturally.
It's the same as when sales people talk to me and intersperse "Well, Mr. wink, you know about this great offer, that will benefit you, Mr. wink, very much. As I said earlier, Mr. wink." - makes me want to end the call right at the 2nd mention.
Which would be quite impolite, tough fella. The nice thing about working in a professional environment is that I don't have to cater to your desires, I simply have to be polite and professional :)
I can't figure out if you're patronising on purpose, or genuinely polite. FWIW I suspect it's the later, and your sorrys and smiles are meant to soften the blow. But I guess that highlights the issue - it's sometimes hard to distinguish between the two, especially when the other side (like me) is used to a more direct communication.