I see there is a small movement towards them for heavy tackle stand up game rods as well. Interesting. I thought they were a fad that would of died out by now. 

 There are a number of advantages to Spiral wrapping.

on overhead rods the line tries to go underneath the rod, it's a basic physics thing. Allowing the line to do this by spiral wrapping it removes the twisting forces you experience when using an overhead. That's why Gimbals are for Overheads as it locks the rod in place to ,are things easier for you when winding etc. you may have noticed spin rods feel more stable under load.

you can use less guides. While it saves on costs it's more an advantage in terms of allowing the rod to perform better. The more things you bind onto a rod the more you affect its performance.

Less guides means less weight which can be a big thing when it comes to many hours of jigging and fatigue is a factor. It might not sound much but trying to swing a weight from a distance is a lot harder when it's right in your hand so saving a few grams or so towards the end of a rod adds up after a few hours of jigging.

They look weird but there is a valid reason for them being around.

 one of the bigger advantages that some boast is that they eliminate rod roll under heavy load and thus reducing wrist fatigue. In my experience there was still some twist on the rod and after 20 minutes on fish the wrist is aching anyways unless your in a harnessed gimbal. I do like them though. 

+1 what Bunny said.

I fish a mix of spiral and standard overhead rods. The Spirals do help with the reel torquing, and I find almost totally eliminate the tip wraps you can otherwise get while jigging with overheads.