Boy, Interrupted

I was raised not to interrupt when people were talking.  I thought everyone was raised this way, but apparently they weren't.  Or maybe they've just abandoned good manners.

It seems more and more (especially at work) I've been surprised at how inconsiderate people can be.  As a real estate agent I get calls from potential buyers with questions about properties they've seen online or while out driving.  They'll ask me a question and before I can finish an answer they will interrupt with another question or statement.  Real estate can have complicated components and contingencies requiring more than a 1 or 2 word answer. 

Recently Spouse & I were out to dinner with friends and the well-meaning waitress kept walking up to the table and interrupting our conversation to ask if we needed anything.  I understand that it may require 2 extra seconds, but can't servers approach the table and allow the person speaking to pause before saying something like "Excuse me, but may I get anything else for you?"  Honestly, I find it rude.

Where is the consideration?  

Where is the politeness?  

Where are the manners we learned as kids?