agree with this.
im the one who actually does the "work", and believe it or not, require some focus to do this. if every message that i currently receive as an email came through as a phonecall, my productivity would drop. i would no longer be able to focus on work, then take some time to focus on following up emails between tasks.
however, i guess, from the client point of view - they just want to find something out striaght away, so i can see why they would see it as more efficient to get an immediate answer with a phonecall.
it feels like two different types of workers.... like project managers vs. programmers ? ( just an example! :) )