I think it's true that Ts aren't busier than other professionals. It's reasonable to expect that emails be responded to in a certain timeframe during office hours. I think the issue is when Ts let that contact extend into their personal time. If all their clients were emailing and expected responses, a T busy with family and other responsibilities wouldn't be able to really read and respond to them all. If they do, they're taking time away from their loved ones and personal life. Some Ts do seem to have little understanding of the emotional weight some emails carry.