The entire concept of crowdfunding is reliant on these websites that facilitate the process. As with any financial instrument those running the scheme, IPO or whatever will be taking a commission. It is this commission that is the important thing to them, particularly in this area of unregulated Internet funding. It is just seen as a more acceptable version of the scroats that try and sell worthless shares for startup companies.
Unfortunately, for whatever reason there appears to be a never-ending pool of people who are sucked in by these "kickstarter" promotions who end up losing money.