There are two vital reasons: to verify the authenticity of a card both for collectors and official play and to ensure you can adequately protect your card with sleeves and binders
Secret Lair x Jaws: Terror of Amity Island Jaws, Relentless Predator - Original card Descent into Avernus (Panic on Amity Island) - $10 Nonfoil / $10 Foil Reckless Endeavor - $7.60 Nonfoil / First Foil Sneak Attack - $5.89 Nonfoil / $5.74 Foil Abrade (You're Gonna Need a Bigger Boat) - $0.25 Nonfoil / $0.25 Foil Blood token $0.20 Nonfoil / $0.40 Foil Total = $23.94 Nonfoil / $16.39 + Reckless Endeavor I'm also ranking this one higher than the technically more valuable horror Furbies because it has a mechanically unique Jaws card
Doubly so when you realize that traditionally all of the things that add oodles of mana to your mana pool default to colorless mana
0-cost deal 15, seems strong
Sure, you want to be fast and aggressive, but theres a rhythm to ita way to read the game and know when to keep pushing and when to hold back
Essentially, if you're ready to be the table's archenemy and your deck has a Blue color identity, Consecrated Sphinx is a time-tested classic