Where we live in France it is sigificantly harder than that, and we do occasionally see water-softening systems being installed. Indeed, there was some sort of system in place in our house when we moved in.
But we took advice from our heating installer, who are a very local company, based in the same village, and they reckoned that there was really no point, for domestic supply, in any of these systems, either real, like the ones you mention, or the 'snake-oil' ones like sticking powerful magnets on your pipes and stuff.
In essence, a modern water heater/boiler can now cope with hard water without any problems, so no worries on that score.
So what else would you want softer water for? Well for drinking and cooking, yes. And that's best managed by a Brita or similar filter in your kitchen. We recently tried one of those, by Brita, that fixes onto the tap and filters on demand, but have been very disappointed by it - measuring by how quickly the kettle scales up it was only about 50% as effective as a jug filter (even with generic cartridges).
Interesting that when I was looking up how hard our water is, I came across this definition used by the Alsace Water suppliers:
Dureté inférieure à 10° F - eau très douce
Dureté de 10 à 20° F - eau douce
Dureté de 20 à 30° F - eau moyennement dure
Dureté de 30 à 40° F - eau dure
Dureté de 40 à 50° F - eau très dure
So as far as they're concerned your water isn't even very hard anyway. Ours is somewhere in the 30-40 range.