Why aren't more climbers using rabbit runners for anchor building, etc.?

i just make one out of cord and it works just fine. prefer this to a loop of cord for anchor building. faster and you need less. probably a hair heavier, but really enough to notice? probably not. for alpine stuff it makes sense to want the rabbit runner though.

that being said if i did buy one it would be from mountain tools since its a dyneema/nylon mix, so better for knots and stuff.

I prefer the classic cordelette with ca. 20 feet of 7mm cord in a loop. I can clip into the shelf above the F8 knot; doing that with a RR is a no-go in my book. Short RR's are useful ice climbing b/c you can thread them through holes and around ice pillars.