No company IPOs if they don't absolutely have to. It's like conceding that you can't make enough profit privately to recoup your investment on any kind of reasonable timescale.
These investors are not going to buy your initial stock and then turn around and dump it because that would kill the value of any stock. Instead they have to believe that they can buy your stock and hold it for 12 - 36 months and it will become more valuable so that if they chose to they could sell it into the market over enough months to not disrupt the price and make a return on the money they invested. They need that return because the people who pay them to manage the fund demand a certain standard of performance or they get fired.
If the goal was to just 'cash out' you have to convince all of these people that you're not really going to cash out in order for them to buy into your IPO. That is hard to do with dozens of new investors.
http://www.rollingstone.com/politics/news/the-great-american...