As Steve’s explanation goes, digital cameras don’t have their inherent color spaces.
In RAW, colors are interpreted later time, and when shot in JPEG it already
gets confined to sRGB or AdobeRGB, according to user’s setting.
And color spaces that digital cameras can respond are wider than AdobeRGB,
and even wider than sRGB. ProPhoto RGB can contain them all nicely, which is
why it is usually recommended color space when it comes to RAW processing.
It is obvious that the color space is much larger than even high quality inkjet priners,
so it may sound absurd. However the point is that capture is for recording or archiving.
The archived color info may be used for a number of
different purposes. So capture and reproduction are supposed to be one thing
and another. Using AdobeRGB for your digital images can be acceptable but
sRGB means quite a loss.