Cronie Capitalism does help as well. When the gov puts it thumb on the scale and clears a clear-enough path, only a fool wouldn't follow the path of least resistance.
Suppose the government did put its thumb on the scale here, how would it impact consumers? Will they now be able to shop for lower prices at a business that earns 1% profit margin or less instead of the 2.6% profit margin that Costco has managed to climb to?
The government is not supposed to be in the favoritism business. When that happens, as we're seeing, there are unexpected and/or unwanted consequences. The government is supposed to level the playing field, not the other way around.
Regulation. Be it local, state and/or federal. The larger the organization, the more resources it has to mitigate / remedy such friction.
The irony? Regulation is also self-serving to gov in the sense it perpetuates ththe gov's need to prove it needs to exit, "create more jobs", etc. But that's another discussion for another day.
Two, lack of national *affordable* universal healthcare. Again, larger companies are better able to fill this gap, offer the benefit, and thus draw better employees, etc.