Lost is a show that throw so much information at you essentially every episode, it needs to be thought about afterwards – so it’s definitely one with needed rewatch value. Similar to how you might forget the beginning of a movie if you leave it half a year to finish off, you forget some of the intricate developments that happen to the Losties that get them to where they are today.
Season 3 especially I find, due to it’s fairly stretched out length and sometimes pointless unravels it becomes hard to distinguish between what is important and what is filler. And in heavily serialized show like Lost it’s sometimes hard to have the brain working tenfold on a late night all the time.
I think, if anyone jumps into it’s final season without, at least some sort if recap; they’d be mad.