It probably depends on the company: Founders and employees may seek liquidity, for example. According to http://seekingalpha.com/article/3746196-ipo-preview-atl

It probably depends on the company: Founders and employees may seek liquidity, for example. According to http://seekingalpha.com/article/3746196-ipo-preview-atlassian-corporation-plc http://seekingalpha.com/article/3746196-ipo-preview-atlassia..., it looks like Atlassian offers 10% in the IPO. But I'm not a financial analyst.