Preferred pricing for large employers, vs small employers, vs individuals never made sense to me except for private insurers to divide up groups to maximize pro

Preferred pricing for large employers, vs small employers, vs individuals never made sense to me except for private insurers to divide up groups to maximize profits. If insurers were simply trying to provide best-value, then every customer should be in the same risk pool and excess administration costs to create and apply different rules for different groups could be eliminated. Instead, all the private insurers create many groups with complex rules, different coverage levels, then have to administer all these slightly different rule sets. That complexity then has to be dealt with by everybody, the customer, the health provider, as well as the insurer themselves. Profits are possibly maximized but value provided to customers and society is destroyed. I think this is pretty much reflected in the roughly 2x per capita costs for private healthcare in the US vs costs for universal care in many other first world nations.