The government does nothing for several reasons. 1) People prefer Walmart and Amazon to driving down town to some mom and pop store. 2) Walmart and Amazon do provide jobs (the quality is questionable) and the government needs its citizens to have jobs. 3) Although people may have lower wages, the economies of scale give people greater buying power. Stores downtown need to pay rent and heat and carry inventory. The money for that needs to come from somewhere.

That being said, the SEC and FTC need to start doing their jobs. They have failed us in the 21st century. We need to rollback all these mega-mergers and stop allowing them to move forward, not just in tech but also in banks and media.