I think it's basically some PM taking a stand at Tesla with the fact that there's just no good estimate possible without knowing the route, so they will always show EPA estimate.

Any sane a Tesla driver changes that to show percent battery instead of range.

As others have said the trip planner is excellent, within a percent or two even in winter conditions driving over passes etc..

Note that range changes a lot more due to elevation, speed, cold etc, compared to gas cars because electrics are so much more efficient.