Where minimum efficient scale is very huge for capital intensive operations, it may be more cost effective to allow one company to spread its fixed costs over a very huge number of consumers, rather than have various competing firms suffer the fixed costs of a minimum efficient scale and have to share a customer base.   There are various industries that are very capital intensive and need large initial investments to operate.  These types of firms are frequently natural monopolies.  Railroads, electric generating companies, and air lines needs tens of millions of dollars in fixed costs.