I think the reason some traditional artists frown upon digital art is that the computer has become the middle man and it interprets your actions. The experiences are quite different and there seems to be greater satisfaction from actually painting rather than doing one digitally.
Its kinda like being at a football game versus watching it at home on your TV.
my 2 cents
No man who values originality will ever be original. But try to tell the truth as you see it, try to do any bit of work as well as it can be done for the work's sake, and what men call originality will come unsought." - C.S. Lewis