The SX-70 was the world’s first truly instant camera, and it comes from a time when things moved a bit more slowly. Slower times, slower film speed. Don’t worry, it still develops as fast as the other films – it’s just a little more laidback about it.
The SX-70 works a little differently to other Polaroid cameras, meaning it needs a film that reacts to light more slowly. That's why it has its own special SX-70 film with a much lower ASA (that's how you measure film speed). Lower ASA film often gives you richer color and texture, which is why the SX-70 is so popular with artists, creatives, and people who use the word "aesthetics" a lot.