There is a mental benefit too.
Without being overly long winded about it...
Imagine you are on a motorway doing 70mph, when you slow to 30 when exiting it feels very slow.
On a track you will be moving at much higher speeds, this will "speed up" your thinking so, when you go back onto the road 60mph will feel slow, meaning you will have more "mental" time do deal with hazards as they arise.
Like I said, this is a very quick outline of the theory but hopefully you get the idea.
All the other stuff about the physical aspects of riding applies as well.