Comment by jrootabega

One possibility is that they only use a small amount of time, mental effort, and context size to go over all of the messages at a relatively shallow level. If there is anything that lets them send the ball back into somebody else's court without fully digesting a message or thread, they will go for it. That other person will then be responsible for the effort of replying at all, thinking about the subject matter, accounting for other peoples' messages, and composing the reply message itself. They also probably further minimize reading intellectual subthreads, and instead keep practical, concrete items at the top of their stack.

Overall, this means that they will sometimes err on the side of being deaf or dismissive.