According to Robert Green :
"Steve Barker LT" wrote in message

By pigtailing you avoid the chance that a loose connection on any one
outlet
would affect the downstream outlets. It is especially important when
using
12-3 to pigtail the neutrals. This way if you have to replace an outlet,
you don't "open" your neutral circuit to the downstream outlets.

If you had to replace an outlet, you'd have the breaker off at the panel,
wouldn't you? Why would you care what happened downstream on a dead circuit
branch?

It's not uncommon to see shared neutral circuits to not be tiebarred
together in the panel. Someone naively turning off one breaker, and
pulling out the outlet breaking the neutral (he doesn't get zapped
unless something is live and pulling power on the other leg) can
result in rather nasty things happening. Especially if the first
breaker is turned back on. That downstream may not really be dead
in a shared neutral.

It happened often enough for our code to require neutral pigtails
at least on shared neutral circuits. As yours does.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.