Because I'm a rifle and rifle accessories whore and like to try as many different things as I can even though the main thing I've learned from my experimentation is that all this stuff makes way less difference than we like to think.
Same reason why I have 223 AR's with 10.5, 12.5, 13, 13.7, 14, 14.5, 15, 16, 18, and 22 inch barrels even though a 14.5 or 16 would probably suffice for my needs.