using tables etc. is the best way to make a site unreadable by anyone using a non-graphic browser, so anyone using lynx. Any blind people using a text-reader etc.
I don't know about other places, but in the UK there's laws being passed which will apply to coorporate websites as they apply to physical premises, in that it's a legal requirement for the owner to make them accessible to disabled people etc. Tables don't cut it.
I can't remember the exact statistics, but predictions are that within 10 years, PC's will be in the vast minority as far as internet connected devices go. It'll be mobile phones, PDA's, watches, MP3 players, Fridges etc. These will have small displays. CSS will be essential to ensuring that all these devices can view content without there being a requirement to re-write the page for every different type of device.
I'm rambling and I'm sure that there's people who have put this a lot more eloquantly than I have, but HTML is for displaying your content, CSS is for making it look good.