Design as an profession is older than the web - it's older than programming. The industry as a whole is intimidated by modern technology, and appeals to non-technical people.

As a result, many of the people coming out of professional design schools, trained in the esthetics of flat, non-interactive design see themselves as 'above' all that 'computer stuff'. This, combined with intimidation, and a massive demand for good design, keeps them from expanding their skillset.