On the flip side, I think the connectors would have been more than double the cost, and likely event more expensive than the cables themselves.
You can even have a round cable with pins radiating out from the center, and the connector would be concentric circles. Then the plug will always go in no matter what.
Manufacturers do. I can't count the number of times that I've seen hardware manufacturers spend four-to-five figures in order to find a way to eliminate a 2 cent part. At scale, even a 2 cent part adds up to serious money.
Because people are always looking for the lowest price for things, so manufacturers have a very strong incentive to reduce those prices. If they don't, then people will buy the competitor's gear that costs 2 cents less. In that sort of market, manufacturers won't raise prices for gear unless they have no other option. If they need to get more money out of it (because of cost increases, or because they want a higher profit margin), then the first thing they'll do is find a way to reduce manufacturing costs. Increasing the price is the last thing they'll do.
We're talking about an industry that in 2014 included about 600 million units [0] - times maybe 4 USB ports per unit, and we're nearing 2.4 billion USB ports. That money adds up fast.
[0] - https://www.statista.com/statistics/272595/global-shipments-...