Push email a necessity?

I honestly don't understand why sooooooo many people on the internet need push email. When Sparrow was released, it was clearly the best Gmail client on iOS. But I remember vividly that tons of people were saying that they can't use it because they need push.

My question for everyone that says they need push.... why? I honestly don't understand how so many people have jobs that require them to see an email the moment it has been sent to them. Really, what jobs do you guys have that waiting 15 minutes for an email to be fetched is impossible.