The Canon XPS driver supports "16 bits per channel" colour printing which renders smoother tones than the standard Canon driver, but you'll need to be printing a photo from within advanced photo-editing software which can work with 16 bit colour (eg Photoshop).
For every day printing and snapshot photo printing you do not need the XPS driver, you'll get no benefit from it.
That applies to most users, hence it's not selected by default.