The example is contrived because there is no content in the table cells. In the real world there will be some content, and suddenly your "width"-attributes are many lines apart and not nicely aligned. This makes is a mess to maintain, because there is no single place where your layout is defined; the information is spread all over the document, mixed with other kinds of information.

Furthermore, separating style info into a style sheet allows you to adapt the style for different devices.