Diane Greene, the CEO of Google Cloud, stepped on stage Tuesday at the opening of the company’s annual customer conference to proclaim that the cloud unit has officially become an enterprise company. On Wednesday, a parade of other Google Cloud leaders continued to promote the technical advantages of its offerings.

But aside from announcing a handful of new customers—something Google Cloud does every year at the event—there are reasons to be skeptical about Ms. Greene’s claims. More than four years after Google’s infrastructure chief Urs Hölzle boldly predicted that the company’s cloud computing business would someday overtake its digital advertising cash cow, Google Cloud has come nowhere near achieving that goal. Both of Google’s main rivals in the market, Amazon and Microsoft, generate more revenue in one quarter from their cloud businesses than Google does the entire year.