Most (if not all) have been updated since the advent of CSS, though.

You may be correct about demand, but it just seems logical to me that when a notable programmer is spending lots of time either coding, or travelling the country speaking at conferences and/or having high-level meetings, etc...basically, busy all the time...the last thing on their mind is "I need to make my website pretty". I think that most of what they host on their site is simply either for their own reference or for the reference of others. I know I've said more than once "just go to my site, it's linked there" when asked a question about something (and I'm the most un-notable there is).