The ALT Example in the Components Document

Is there a reason why we use keyword abreviations like ALT instead of full
terms like alternative text?    The following rephrasing of the ALT-Example
seems to be a little simpler although more wordy.

-- Technical specification defines the alternative text attribute (ALT) of
the HTML image element (IMG) and why it is used as a substitute for the
graphical image to accomodate indiduals who cannot percieve images
-- The guidelines, WCAG, ATAG, and UAAG define how alternative text is
implemented for accessibility
-- Authoring tools allow, encourage, and assist developers define values
for alternative text in specific documents
-- Developers provide the the appropirate wording for descriptive
alternative text
-- Evaluation tools help check for the existence of alternative text
-- User agents provide human and machine interface to present alternative
text
-- Assistive technologies provides human interface to transform alternate
text into various modalities
-- Users know how to get the alternative text from their user agent and/or
assistive technology as needed