Because the point of it is the exchange of memories between a Harry who has all that support and is emotionally healthy, and a canonish Harry whose crappy life has left him motivated to succeed but not really able to do social connections and all too ready to take the blame/responsibility/pain for any problem that breaks through his isolation to be percieved, making them both stronger. Well, assuming the Mirror is scrying another place with the viewer's wish as focus, like a pensieve scrying the past with
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"Anko, what you do in your free time is your own choice. Use it wisely. And if you do not use it wisely, make sure you thoroughly enjoy whatever unwise thing you are doing." - HymnOfRagnorok as Orochimaru at SpaceBattles
woot Med. Eng., verb, 1st & 3rd pers. prsnt. sg. know, knows
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"Anko, what you do in your free time is your own choice. Use it wisely. And if you do not use it wisely, make sure you thoroughly enjoy whatever unwise thing you are doing." - HymnOfRagnorok as Orochimaru at SpaceBattles
woot Med. Eng., verb, 1st & 3rd pers. prsnt. sg. know, knows