The power in the magic words "Thank You"

I was initially going to post this as a facebook ‘rant’ but I decided against it and thought to make it an actual post. Have you come across people that are just not courteous? People that seem to have deleted the simple magic words (please, sorry, thank you ) from their vocabulary?

I witnessed a not-so-pleasant experience this morning. An old colleague (Miss B) who had not contacted someone I know ( Miss A) for years, unexpectedly reached out this morning. Miss B didn’t bother with pleasantries- she needed a favour. Miss A was saying to me that it was such a pleasure to hear from Miss B after such a long time and she was happy to help her out since the favour was easily within her reach. So, Miss A took a few minutes off what we were working on, excused herself to go attend to Miss B’s errand. When she was done, she chatted with Miss B, gave her all the information she asked for, and that was it. Yes, that was the end of the conversation. Miss B read the message (thanks to the advance in technology you can tell when someone reads your message) and didn’t respond. No acknowledgement, no thank you, no goodbyes. Miss A isn’t surprised as it’s not the first time she has had such an experience. But I am stunned.

Do you think I’m being too sensitive? Is it such a big deal to say 'thank you' when people do things for you? Please let’s discuss this.