1. You can engage in Triangle Financing and make your investment crowdfunding an easier journey.
2. Having a product lets your potential investors know you're serious and further ahead than just having an idea.
3. The hardest part of crowdfunding is attracting the crowd. When you have a product don't just attract the crowd to invest, invite them to buy your product. That is called generating revenue. Revenue is the best capital in the world.
Assuming you have a good team, a truly investible company, and a story that is compelling to a crowd of investors/customers who are, for the most part, one and the same, entrepreneurs need the wherewithal to fund an investor/customer acquisition campaign using expert marketing resources.
It is false to think you can solely depend on a funding portal's investor base to acquire investors to your particular opportunity and steer clear of funding portal's that promote the size of their investor base to win your business.
In another Q&A posting by @startmotionmedia , they indicate that "Even the viral projects we’ve run only tend to get a max of 15% of their backers from the platform (Kickstarter)." Seems that platforms can only do so much and that the entrepreneurs really must bring their own networks?