Then why do we need a breather to begin with?

There'll always be a small amount of gas that blows past the rings on the power stroke, due to the pressures involved. Without a breather the pressure would slowly build in the crankcases and reduce engine performance.

So why do enduro racers run a hose from the breather to the oil fill?

An engine breather should run to a catch tank.

Aye, but then some tanks then have either a vent to atmosphere or some then have another line to the oil filler.

Kind of pukka cool...might get one..lol

You can just vent it to atmosphere,But you have to keep an eye on it,empty it if necessary.