I suspect that when people hit "reply to all" to a message from a
list they
generally want the reply to go to everyone who received the original
message,
not "just" to the list. They don't want to worry about which of those
recipients are on the list and which ones are not.
Precisely! I think that's exactly what the proponents of MFT are
arguing.
But I think they _do_ want to worry about whether their replies are
going to "all" or to some other set of recipients. And MFT can cause
the replies to go to some other set of recipients without the responder
realizing this.