I don't think there is a technical reason. It's probably not something they'll do for a while because it probably requires some significant reorganization of the compiler and making a passably fast implementation is probably quite hard (the Go community places a premium on fast compiler times, rightly or wrongly). Also they seem to value predictable optimizations. Not sure how keen they would be to add an optimization that works until a seemingly inoccuous code change prevents the compiler from guaranteeing that all elements in the slice have the same concrete type, making performance (probably) significantly worse.

Again, I don't necessarily agree with the Go team; I'm just guessing the are some of the concerns they're weighing.

Ah I misunderstood the previous comment. Sure, if you have a list of pointers to values that satisfy a given interface, dispatching at compile time would not be trivial.