I'd say it's just a way to identify a degree of necessity.

Humans are not machines - when a request times out, we don't just resubmit and try again, there are other consequences to this failure to respond.

The lack of respect for your peers and subordinates is one.

You don't want very passive people working for you. You want people who can route around what you're busy doing and manage their own projects.

If you are absolutely critical to whatever they need to do, they have to be managing you about it, not just sticking more work on your lap and waiting for it to bounce off. Which means more than sending an email and never following up.

i am only refering about requests that involve more than one person and not about multiple requests from one person. E.g. A feature request by more than one person.