Also Germany has a limit of 252, IIRC, and I expect the majority of long freight trains passing through Switzerland to be international services. There are plenty of old axle counters in operation around Europe because ultimately it's a limitation more in theory than in practice.

Along with the steep gradients, you have to remember there's far more passenger services on the lines, so pathing constraints force freight services to be shorter (you can't have them accelerating that much slower than passenger services, or they start taking up a disproportionate amount of capacity on the line).