Why don't people contextualize their e-mails more?

E-mail is a scourge for many people -- 89 billion of the business variety are sent every day, no one can stop checking it, and people devour articles about time hacks as relates to e-mail.

Here's what I sometimes wonder: why don't people contextualize their e-mail?

Here's what I mean by that: why not open any new e-mail with a line explain the time sensit…