That's why you need this!from a performance point of view, it doesn't make much difference.
actually, any type of tip is going to decrease your performance slightly. in fluid dymanics terms, a tip is what is referred to as a rapid expansion. a rapid expansion occurs any time the diameter of the pipe sharply changes. a pipe open to the air is a type of rapid expansion. you'll always have one of those. by adding a tip, you are essentially making it into two rapid expansions - both of which cause turbulence and resistance to flow. (one where the diameter changes from the pipe diameter to the tip diameter, one where the tip changes to open air)