Closure. The entirety of the flashsideways were about the characters working through their issues- Jack proving to himself he 'had what it takes' to be a better father than his father, Kate finding people who accept her for what she is, Sayid learning that he is a good person and he didn't need to cling on to Nadia to validate himself, etc.
But...is this good?
Lots of stories have characters that die and live. But we don't have huge dead world scenes just so they can have happy endings.
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SuperNiceDog - 1, pjbasis - 0