Why Quaternions?

Hello, I’m wondering why does Unity use Quaternions?
Since I’m almost every time use Euler angles (and I’m sure I’m not alone), why do we need Quaternions?

Thanks.

Quaternions were invented to overcome the Euler problem of Gimbal Lock.

Quaternions are just 4-component vectors, with xyzw.

They are more expensive to create than matrices, but are much cheaper to update once created.
They are only 4-float structure, whereas matrices are 16-float. This reduces the size of data during runtime.