Individual cards are skyrocketing in price, and sealed products are becoming increasingly difficult to get hold of, with scalpers and flippers buying as much stock as they feasibly can and reselling it at far higher prices
Balthier and Fran's last ability doesn't give you any additional main phases
Transmogrify is already a card with a similar ability in red, and "Polymorph" decks that turn weaker creatures into unexpectedly powerful ones is a fun strategy that could take advantage of this
Basically, for a flashback card to be playable, the front half either has to be close to on-par for its effect, so the flashback aspect of the card is a bonus / afterthought, or the reward for getting the card in the graveyard is good enough that you don't mind building around a card that's not that great in your hand
You get to have a card for the first creature that dies a turn, talk about value