Concentration is the default in an unregulated environment. Sure pure monopolies with 100% market control are rare but concentration is rampant. A handful of companies dominating tech, airlines, banks, media.
Concentration seems much more prevalent in heavily regulated markets e.g. utilities / airlines. In many cases regulators have even encouraged this e.g.finance.
There is no default for unregulated markets. It's a question of whether the economies of scale outweigh the added costs from the complexity that scale requires. It costs close to 100x as much to build 100 houses, run 100 restaurants, or operate 100 trucks as it does to do 1. That's why these industries are not very concentrated. Whereas it costs nowhere close to 100x for a software or financial services company to serve 100x thee customers, so software and finance are very concentrated.
The effect of regulation is typically to increase concentration because the cost of compliance actually tends to scale very well. So businesses that grow face an decreasing regulatory compliance cost as a percent of revenue.
You are comparing Apples and Oranges. You just can't compare the barrier of entry for Software business and an Airline, even without any regulations. It's just orders of magnitude more expensive to buy an airplane than a laptop, and most utilities are natural monopolies so they behave fundamentally different.
I can't and I didn't. I never said anything about barriers to entry. I'm talking about concentration here and why the market is dominated by airlines with hundreds of planes instead of airlines with 10 planes. Barriers to entry are inevitable in capital intensive industries.
Home building is interesting because I think a major blocker to monopoly-forming is the vastly heterogenous and complicated regulatory landscape, with building codes varying wildly from place to place. So you get a bunch of locally-specialized builders.
Regulation can increase concentration in a high corruption/cronyism environment
— regulatory capture and regulatory moats. There is plenty of that happening.
In building, I think we have local-concentration, due to both regulatory heterogeneity and then local cronyism - Bob has decades of connections to the city and gets permits easily, whereas Bob’s competitor Steve is stuck in a loop of rejection due to a never ending list of pesky reasons.
Concentration is not monopoly, and furthermore your comment does not begin to address the critical part of parent’s comment : “does not last very long”
Inequality at a point in time , and over time , is not nearly as bad if the winners keep rotating
