The startups being delivered by Silicon Valley aren’t impressing Wall Street, according to a recent article in The Wall Street Journal.

The article reports that over the past five years, venture investors have channeled tens of billions of dollars into the largest startups, “betting that stock-market investors would look beyond companies’ heavy losses and embrace their visions of industry disruption.” But so far, the results have fallen short, it adds: “Private investments in six of the 10 best-funded U.S. tech startups to go public since 2015 have fallen from the peak levels they hit in funding rounds before the companies’ stock debuts, according to a Wall Street Journal analysis of data from research firm Pitchbook.”

The same analysis showed that late-stage private investors in those six companies would have fared better with an investment in the broader market, citing the examples of Uber and Lyft—both of which have experienced share price dips since going public.

But despite growing skepticism, the article says, cash is still flowing in and “every few days it seems, the Silicon Valley startup machine elevates some new company to a valuation over $1 billion, often aiming for a rich IPO some years down the line.” Startup investors are wagering on company founders that appear to have a compelling vision for the future of tech “that could drive wholesale industry change.” But public investors, the article points out, “look at projections for cash and earnings. They’re more inclined to fill their portfolio with financially healthy companies that will perform well in the foreseeable future.” The difference in viewpoints isn’t new, but the article explains that the “balance has shifted over the years. Stock-market investors a generation ago were far more forgiving.”

Today, the article says, companies are staying private longer and turning to private funding for their early stages of growth. “Public investors,” it adds, “tend to want something more predictable by the time companies begin trading.”