[makeitdouble]

Price and maintenance. I asked while in France, and while you can buy them

- you need an electric plug, and builders tend to avoid putting them in the toilets or aren't asked for in the first place.

- once you have them, the water clogs the thin pipes with calcium apparently. So every one/two year we'd have to replace the tubes.

[MajimasEyepatch]

The calcium issue would mostly depend on the hardness of your water, right? So that would probably vary by region.

[makeitdouble]

It is, and Japanese water is overall pretty soft so it helps in that regard.