Not sure if the "why" is the same for everyone?
But for me, it's because you can't walk into a stihl dealer and buy brand new 064 anymore.
If 064's were still at dealers available new, and sat side by side, with a 461, and they weighed the same, but the 064 had more power then yes, I'd walk out with a new 064.
That is not the case thou. So a 461 it is.
064 is a 30 year old saw, yes it can be rebuilt, no matter what you do to a 064, it's still a clapped out 30 year old saw, and not new anymore. Nothing like a brand new saw.