[sjamaan]

Presumably you'd be interested in any feedback, and not everyone CCs the original author in their reply.

[nolist_policy]

Reply-to-all is the standard policy on most mailing lists. Especially on -devel lists since you'll pull in (CC:) people outside of the mailing list (cross-project) into discussions from time to time.

[Avamander]

I know more than one occasion where that has gotten an angry reply.

It's also not the default in many clients. It's tedious and error-prone.