Smoke deflector

[PA DL]

I'm in the process of quitting smoking cigarettes.
In that I was thinking about this part and what do it do?

[stopintime]

If mounted on your face you can't smoke. If mounted on the it directs the cold air to the heads/cylinders. I think that's it. I've taken mine off.... and quit smoking.

[PA DL]

HeHe it's not on my bike anymore either.
But it got me thinking, why do Ducati calls it a smoke deflector?

[PA DL]

Here is one fitted, do I need it? If so why?
The second question, if, No you don't need it, why did Ducati bother with fitting it in the first place?

[Speeddog]

It does a pretty good job of keeping crap from being thrown off the front tire up into the frame and lower steering stem bearing area.