Take the fact that the United States ranks 20th in the world in internet speeds. Greater, faster connectivity is the sort of public good that could improve access and spur economic activity for everyone. There's a social, public interest. There is *not* an economic interest for the couple of telecom giants that are already delivering enormous profits to their owners and top stakeholders.
Take research, which covers everything from microelectronics innovation that spurs growth and enables better products and competition in tech sectors, to health research which develops new medical techniques or informs public health policymakers. These are things that industry alone can't do, not because they are evil, but because they don't have nearly the same luxury for risk in their R&D as they try to push out products and outsell their competitors.
Take education, which most of us do believe is a public good. The public has an interest in an educated citizenry aware of our country's history and knowledgeable about its civic institutions. Companies just need technically proficient workers, which is hardly the same thing.