The crowds are what everyone seems to be concerned about, and I cannot think of why they are missing.
It is not lack of interest because the matches are being followed very keenly and cricket is the focal point of several discussions and day to day conversations.
A theory that has floated into my head, which I hope is proven wrong, is that while T20 and IPL may not have reduced the general interest in Test cricket, it may have redefined what constitutes a 'stadium experience'. So unlike before where watching a match in a stadium for 6 hours with periods of highs and lows and passive stretches in between was fun, it may now be that a 3 hour burst of energy and madness is what is fun.
Just a vague theory, there may be nothing to it. Or so I hope anyway.