Asphalt/concrete isn't either. Gravel or packed dirt is way better.

That said 30km/day is very real, even in mountain country. It takes 6-7 hours, the rest is resting/gawking/laying on a mountain watching the sky (or trying furiosly to find that effin trail on osmand). I walked that a few times a week when I lived in Montenegro, and that was 50/50 roads and mountain trails from sea level up to 700m-ish elevation and back. No fancy shoes, no prep but for a hat and couple bottles of water. After a third walk or so it isn't even exhausting.