Tables are for displaying tabular data. If you wanted to lay out a calender for instance, sure you could do it with block-level elements and CSS, but it's technically valid to use tables for it.

When it comes to document structure, layout etc... you're not displaying tabular data (unless the page is just a huge sheet of data). Correct, table-based layouts will be valid in any HTML, including XHTML 1.1 at the latest, but for people with disabilities, they sometimes linearise tables in their browser. They learn to read from this method and thus it works for them. Table-based layouts would look very strange in this form... although it would appear in the same order, the page would be in bits and pieces.

Table-less layouts are on the increase, as more people are realizing the benefits. e.g. you could have 5 <div>s and an external stylesheet as oppose to a <table>, 3 <tr>s and possibly 10 <td>s. Sounds bare minimal, but when you think that the stylesheet is cached for most users, loading times can be reduced dramatically by using CSS where possible. Especially if you have multiple pages with the same structure and layout.

I'm not an article writer and so Ima shush now... but is definitly good practise to use CSS-based layouts rather than table-based