The table tag was originally intended to as a way to represent data in rows and columns, like a spreadsheet. Along the way, however, it was hijacked and used as a navigation system. This, technically, is an abuse of tables.
The alternatives, such as using div tags in combination with CSS positioning, have only just become viable with the advent of Gecko-based browsers, IE5.5 and Opera 5 becoming free.
However, the table navigation system is unlikely to die, since lots of people believe it to be the only way to produce a viable navigation system (apart from frames), and they know nothing of style sheets. And, of course, there is the problem of old browsers, which lack the proper support of div and CSS. Particular in this problem is Netscape 4, since a lot of users haven't upgraded to Netscape 6 (I don't really blame them, it is based on the unfinshed Mozilla code. - Don't take that the wrong way, I use Mozilla every day!). These problems will ensure that table-driven html sticks around for a while.