The premise of the XHTML 1.0 Transitional variant is to take advantage of XHTML features including CSS but to make small adjustments to the markup for the benefit of those viewing pages with older browsers which cannot understand CSS. Older body attribute support includes bgcolor, text and link.
The XHTML 1.0 Transitional DTD includes everything in the XHTML 1.0 Strict DTD plus deprecated elements and attributes.