By the same reasoning, the most valuable companies should be the dominant suppliers of food, water, electricity and maybe gasoline and basic internet connectivity.
Wait, what was your point?
No company is as dominant in any of those areas as Google is in its area, or they probably would be. Water and electricity are often public utilities; while there are big food companies, there's no parallel to Google; there are a number of major oil companies, but no one single dominant one -- but those of the many in the top tier that are publicly traded are valued highly (from tens of billions to hundreds of billions), and several are not public so that no public valuation exists.