They offer unparalleled artistic freedom
Since you can do this at instant speed, dumping mana into Gretchen Titchwillow just before your last opponents end of turn is a great way to maximize your resources while keeping everything open for a well-timed counterspell
Aetherdrift has yet another Lotus for players to consider, and it is very unclear whether this card is broken or terrible
Special Summon spamming became a normal strategy, Tribute Summons barely existed at all, and monster removal cards eclipsed high ATK/DEF in usefulness more than ever
After it inevitably dies, you can return it to from the graveyard to your hand if you dropped a Swamp
For my money, this is a nice payoff with some big upside, but having the downsides of needing to connect without any built-in evasion plus relying on your opponent picking a good thing for you to reanimate makes this too difficult to use