During the Dot-com Boom, allocations of shares in hot IPOs were highly sought after, as investment banks seemed to consistently price the offerings to guarantee a pop in first-day trading, and award allocations to their favoured clients. Effectively, the investment banks were under-pricing the shares such that the company going public "left money on the table", which got picked up (at relatively low risk) by the i-banks' preferred clients.
Companies seem to have grown wise to this and started putting more pressure on the i-banks to ensure they don't end up leaving money on the table (c.f. Facebook, Pure Storage). Therefore, the i-banks' favoured clients are less interested in taking IPO allocations, so the i-banks need to widen the net to find more investor demand.
1: http://www.wsj.com/articles/SB108328345314098183
2: http://www.cnbc.com/2014/08/19/es-took-off-but-the-auction-d...