“You want to stay private as long as possible,” Edwin Chen, the founder of Surge AI, recently told DealBook. His company, he said, has about a billion dollars in annual revenue and is definitely not considering an initial public offering right now. Despite a soaring stock market, an increasing number of executives seem to share Chen’s philosophy: The number of U.S. public listings dropped from a peak of 8,090 in 1996 to 4,010 last year, according to data from the World Bank. Fewer companies are filing for I.P.O.s, and more public companies are being taken private. His plan focuses on...