Are they somehow more expensive in the US? 40A 230V rated ones cost something like 30-50 € around here which doesn't feel that expensive to me. I'll admit it's considerably more expensive (~4x the price) than a standard breaker, but it's still more like a rounding error in overall costs.
Although EVSE's projection doesn't require you to periodically trip the GFCI so it doesn't get stuck, which is a major plus.
I might've been unclear, I don't mean 230 V by itself, but three-phase distribution. The standard socket is labeled either 3x16A 230V alternatively labeled 380V 16A. Typically uses an IEC 60309 plug that looks like this:
Three phase has other benefits besides just more power, the US has it with their lower voltage as well, but typically reserved just for larger buildings.