Leaving aside debates over the quality of the cricket, there is no doubt the crowds have been terrible.
Even for the supposedly bigger games they have been wanting. No doubt they will pick up in the Super-8's but thats little excuse and there is no guarantee that sell outs will occur.
Circumstances such as high ticket prices and mid week games have been suggested but I would say that it was obvious crowds would be poor before the tournament was close to bginnning.
a) I would guestimate the cricket playing Carribean has a total population of less then 6 million people. Far too few to adequately support an event of this size.
b) The fact that the games are being played on seperate small islands across a massive area means that it is very difficult for local fans to travel to different games. For example where I lived in the UK within a couple of hours drive there was Headingley, Trent Bridge, Old Trafford, Durham etc. Obviously other countries are far more spread out but it is still easier to travel to different grounds than in the WI.
c) Islands with tiny populations are asked to pack grounds. It just never was going to happen.
d) The reliance on tourists was a business gamble. For a tournament to be successful it must have local foundations with tourists as a bonus. Also the geographic location of the WI and the tournaments timing is poor. Apart from the UK and mainland North America, pretty much everone else has at least 2 flights and massive travel effort to get there. Its off putting. Also add into the fact that it is after the Ashes series and you suddenly have less of the biggest cricketing tourists (England) traveling.
Quite clearly, the tiny crowds should have been expected. In fact there was never any other possibility and the tournament planners and the ICC should have recognised this early.