All the same reasons as to why Negate is very strong despite not hitting creatures also applies to Spell Pierce
Whether it's EDH, a throwback to 2012 Standard, or Pioneer, casting Grisly SalvageGrisly Salvage will stock your graveyard up and give you a lot of flexibility in terms of how you want to develop your mana or your battlefield
Unlike Misty, this card does not rely on coin flips but rather attaches the Energy immediately from the Energy Zone
EDHREC players, for example, run this pretty frequently in Tinybones, Trinket Thief, Tinybones, Bauble Burglar, and Tergrid, God of Fright, all commanders that excel leading decks that aim to whittle opponents down to zero resources as soon as possible
(2019-10-04) When casting a spell as an Adventure, use the alternative characteristics and ignore all of the card's normal characteristics
If you play as much Commander as I do, I recommend keeping those cards in a specific box or in a section of your storage container of choice