for me , the butt of the split grip makes for better two-handed casting , and yes , like everyone else , i want my rod to be the lightest it can be , splitgrips do that ! plus i never have my hands in the middle of the grip anyway , i palm my reels , just wanting a 2"-3" rear grip for my hand that goes below the reel seat 

But hey, the companies are making good money with this gimmik

It's actually the opposite. A properly fitted split grip is more labor intensive, thus negating any percieved savings that a couple cork rings can produce.

Although the increase in sales volume probably more than makes up for any adjustment in the unit cost of production.