It is desirable to separate style from content in the XHTML site coding. The reason for this is that all of those style tags get in the way of the accessibility features. The following paragrapg is directly copied from the W3C at W3C Accessibility features of CSS
CSS benefits accessibility primarily by separating document structure from presentation. Style sheets were designed to allow precise control - outside of markup - of character spacing, text alignment, object position on the page, audio and speech output, font characteristics, etc. By separating style from markup, authors can simplify and clean up the HTML in their documents, making the documents more accessible at the same time.
The main reason why all developers should accept Cascading Style Sheets is that under the traditional methods of website design a layout had to be copied into the relevant tags on every single page that it was required. With the CSS system the one single file with the .css extension contains the styling instructions and each separate page is connected to the style sheet. Therefore each single change made to the style sheet effects all of the connected pages simultaneously. Believe me, this saves a lot of time.