Rejuvantion is for those without LOVE LETTER.

Sure, you COULD get a good nights rest:

But who can rest when we got a Love Letter?

Love Letter does the same basic function of normal rejuvation, only less so, as I recal, rejuvation heals 30. (40 with Serena's Parents) This does 20. Still, your saving a Power Card (yes you are discarding an item) but I think it all balances out.

See, with Love Letter, you could drop all 4 into play, and have them out of your hand, and saved up for when you really want them, power can be destructed and so can items, BUT item destcution is not as common. Also several monsters can work to help you get out items (Zoisite). Also, unlike Good Nights Rest - this is a one card drop - not a two card drop. With Good Night Rest, you must play that AND discard your power card. With Love Letter, its instant Love!