I guess because it makes them more visible when you're decreasing on top of one another? Because it would be like K x sts, decrease, k1, turn; k1, decrease, k to end and it would become a pile of ugly decreases, no? Maybe because this is a heavier yarn with a larger gauge, too, I was worried it would be really obvious (before I realized the hood would completely cover it anyway.) The shaping seems to look just right with the hood doing only the RS rows, though, although I had to fudge the picking up quite a bit, but that's a chronic problem for me.
I don't know why, though, really, that's just what I was told. I've yet to encounter a pattern that has them explicitly written that way, usually it's "on next and every following RS row" but this is only my second neck shaping I've ever done too.
I have another question while I'm at it, though. Any reason not to do a 3-needle bind-off for the hood? It's worked flat back and forth with some increases yada yada for 13-1/2 inches, then the make-up instructions say to seam it but I don't see why I couldn't just split the stitches on the bind off row as if I was doing magic loop (assuming I smash the right sides together, of course) and do a 3-needle bind-off? Sounds right in theory and it came out lovely on the shoulders.... Thanks again!