Illustrator has an additional concept of swatches - where the colour properties of objects are linked to a swatch object. Swatches can be changed, changing all objects/lines/fills/gradientstops that reference them. 

This is extremely useful in complex illustrations where you might have several colours that mean things, but need to adjust them later in the process.

A spot colour needs to be defined like a swatch, so that the one definition can be used identically across many different objects, and later used as a separation. 

That also allows artwork to move between colour spaces, as each swatch can have a representation defined in each colour space. 

That is the real value that the downloadable profiles and swatch libraries provide -- the ability to match output from different devices eg. screen (RGB), web-safe (RGB), inkjet (CMYK),web offset lithography (CMYK with colour profile) and spot colour reproduction.