Tableless web designing is the ways of designing web page without using HTML tables. Here are a few reasons as to why you should go tableless coding:
• The current W3C standards dictate the use of tableless design.
• Tableless website or tableless xhtml loads fastly in the browswer so it saves lot of time of end user.
• It is easier to make global changes to the layout with the use of CSS. That is, if the coding is properly done, of course.
• Web site accessibility for people with special needs is done more easily with the proper implementation of content into XHTML documents. In tableless coding, CSS is used only for the layout and style.
• Now a days due to rapid development in the web technology all browsers support CSS for controlling web layouts. So your site will be compatible with most any browser.
• Due to proper use of XHTML and CSS Unnecessary code is easily eliminated making for a sleeker and we get more manageable code.
• Tableless formats make it easier for search engines to index a web site. Tableless websites are seo friendly.
That why In web 2.0, web designers and HTML developers are providing service of Tableless Design, Tableless XHTML, Tableless CSS. Though tableless formats are being widely used for page layout control, it does not necessarily mean that tables are not being used anymore.

I would like to correct your last point of “Tableless websites are seo friendly”, it is not that the website which has table layout is not indexed to google, google only needs the code which is clean and you can make your code clean although you’re using tables. If you think that only tableless layouts are indexed to google then I would like to suggest you to do some more gooogle…
Actually this point is proven by many researchers and I am agree with you Good websites with table layout are indexed by google.