If not now, eventually they must be or must have been "doing startups" because all businesses begin as startups. It's in the name, a startup is a company that is just getting started. Some eventually grow up into the titans of industry that we all know.
The parent is wondering why don't we see more entrepreneurs founding companies that look like they could become the next titans of industry. It seems to me that their companies either don't exist, or are currently invisible because they haven't begun gobbling up market share.