The tube takes the crankcase blow by, which can have oil in it, out under the car.
The oil tends to coat the firewall and is more prevalent in cars with loose rings and the wrong baffles in the oil filler tube. Ford went through several variations of oil filler tubes while trying to minimize the oil coming out. I believe an article on this was run in one of the national club magazines.
From the looks of this guys car he is trying to protect a lot accessories.
Can we count them all? (this is just for fun on a cold day and I am not picking on the guy or saying anything here is bad)
Remote starter switch
battery disconnect
alternator
temperature gauge
manifold heater
I do not know what the little white thingy is in the lower right. Something is odd with the wires running to the horn and or lights on the lower left. I am guessing he has turn signals too.
I am impressed the car has engine splash aprons.
Looks like the guy drives his car, which is what is ment for doing.