why a main() function?

[Diez B. Roggisch]

bearophileHUGS at lycos.com wrote:

> Others have already told you the most important things.
> 
> There is another secondary advantage: the code inside a function runs
> faster (something related is true for C programs too). Usually this
> isn't important, but for certain programs they can go 20%+ faster.

I totally fail to see why that should be the case - for python as well as
for C.

So - can you explain that a bit more, or provide resources to read up on it?

Diez