A Not long ago, if you were a young, brash technologist with a world-conquering start-up idea, there was a good chance you spent much of your waking life working toward a single business milestone: taking your company public. Though luminaries of the tech industry have always expressed scepticism and even hostility toward the finance industry, tech’s dirty secret was that it looked to Wall Street and the ritual of a public offering for affirmation — not to mention wealth. But something strange has happened in the last couple of years: The initial public offering of stock has become déclassé. For start-up entrepreneurs and their employees across Silicon Valley, an initial public offering is no longer the main goal. Instead, many founders talk about going public as a necessary evil to be postponed as long as possible because it comes with more problems than benefits.

B “If you can get $200 million from private sources, then yeah, I don’t want my company under the scrutiny of the unwashed masses who don’t understand my business,” said Danielle Morrill, the chief executive of Mattermark. Silicon Valley’s sudden distaste for the I.P.O. — rooted in part in Wall Street’s scepticism of new tech stocks — may be the single most important psychological shift underlying the current tech boom. Staying private affords start-up executives the luxury of not worrying what outsiders think. It also means Wall Street is doing what it failed to do in the last tech boom: using traditional metrics like growth and profitability to price companies. Investors have been tough on Twitter because its user growth has slowed, on Box because it remains unprofitable, and on Zulily when it cut its guidance for future sales.

C Scott Kupor, the managing partner at the venture capital firm Andreessen Horowitz, said in a recent report that despite all the attention start-ups have received, tech stocks are not seeing unusually high valuations. Their share of the overall market has remained stable for 14 years. Private investors, on the other hand, are making big bets on so-called unicorns — the Silicon Valley jargon for start-up companies valued at more than a billion dollars. If any of those unicorns flops, most Americans will escape unharmed, because losses will be confined to venture capitalists and hedge funds.

D The reluctance — and sometimes inability — to go public is spurring the unicorns. By relying on private investors for a longer period of time, start-ups get more runway to figure out sustainable business models. To delay their entrance into the public markets, firms like Airbnb, Dropbox, Palantir, Pinterest and Uber are raising hundreds of millions, and in some cases billions, that they would otherwise have gained through an initial public offering. There is even an oxymoronic term for the act of obtaining private money in place of a public offering: It’s called a “private I.P.O.”

E The delay in I.P.O.s has altered how some venture capital firms do business. Rather than waiting for an initial offering, Maveron now sells its stake in a start-up to other, larger private investors once it has made about 100 times its initial investment. But there is also a downside. When the unicorns do eventually go public, the biggest winners will be the private investors that are now bearing most of the risk. If you invested $1,000 in Amazon at its I.P.O. in 1997, you would now have nearly $250,000. If you had invested $1,000 in Microsoft in 1986, you would have close to half a million. Public investors today are unlikely to get anywhere near such gains.

F Just 53 technology companies went public in 2014, which is around the median since 1980, but far fewer than during the boom of the late 1990s and 2000, when hundreds of tech companies went public annually. Today’s companies are also waiting for longer. In 2014, the typical tech company hitting the markets was 11 years old, compared with a median age of seven years for tech I.P.O.s since 1980. Initial public offerings were also ways to compensate employees and founders who owned lots of stock, but there are now novel mechanisms — such as selling shares on a secondary market — for insiders to cash in. Still, some observers cautioned that the new trend may be a bad deal for employees who aren’t given much information about the company’s performance.

G “One thing employees may be confused about is when companies tell them, ‘We’re basically doing a private I.P.O.,’ it might make them feel like there’s less risk than there really is,” said Ms. Morrill of Mattermark. If the delay in I.P.O.s becomes a normal condition for Silicon Valley, tech companies may need to consider new forms of compensation for workers. “We probably need to fundamentally rethink how do private companies compensate employees because that’s going to be an issue,” said Mr. Kupor.

H During a recent presentation, Marc Andreessen told the journalist Dan Primack that he had never seen a sharper divergence in how investors treat public- and private-company chief executives. “They tell the public C.E.O., ‘Give us the money back this quarter,’ and they tell the private C.E.O., ‘No problem, go for 10 years,’” Mr. Andreessen said. “Private valuations will not forever be higher than public valuations,” said Mr. Levitan. “So the question is, will private markets capitulate and go down or will public markets go up?” If the private investors are wrong, employees, founders and a lot of hedge funds could be in for a reckoning. But if they’re right, it will be you and me wearing the frown — the public investors who missed out on the next big thing.