Originally Posted by tbzep

It makes me think that since they were smaller and cheaper to fly, they were built more often instead of being left in the packaging. Additionally, they were likely flown a lot more often with single standard motors compared to clustering. With lots of flights comes rocket eating trees, thermals, and damage, especially since you could stuff a C6-x in them. They might not have been stable with a C6, so they either crashed, or hit escape velocity.