Thankfully it’s changing a bit. I’ve noticed that newer Ford and Dodge full sized pickups use amber turn signals. I assume that these vehicles don’t sell very well in places that require amber turn signals (Europe).

Meanwhile, VW, Audi, BMW, Land Rover, and Mercedes all modify their amber European turn signals to red to sell in the US. For some reason, they go out of their way to make 2 parts instead of 1 for many of their models.

I think it’s a styling thing rather than a cost thing now. Back when taillights in the US were a single bulb on each side, cost was a driving factor. Now with complex LED taillights, I think it’s something else keeping amber out of our indicators.