But as noted previously, sometimes I activate Siri accidentally

by saying something that only
sounds to her like "Hey Siri, something-or-other..." Once in awhile what she says back then is almost as good standup comedy, so it's more or less worth that experience.
Honestly I didn't care if Apple wanted to practice on what I was mumbling when Siri ended up saying stuff like "I can't find that album". Maybe I'd have been embarrassed if she had managed to repeat what I actually said after I had accidentally activated her, for example if what followed what she heard as an activation had been my pretty inventive cursing over having dropped a spoon into the pasta sauce... but I can understand how people want to be assured of not having a domestic quarrel (or the make-up session later) recorded for all posterity.