BTW AFAIK those thermosolar thingies used in Israel are quite good but they - at least the ones I am familiar with, common in Tunisia also - have anyway a supplemental electric resistance and are anyway only suited to self standing homes or very small condo's that have a flat (terrace) roof.
And anyway in the same hypothetical 24 flat condo, 6 floors by 4 flats, you would need 48 pipes + 24 electric ducts going to the roof, but most lower floors flats (first, second or third floor, maybe also fourth) would be too far away so you would need a third pipe (24 of them) for circulating the hot water, and of course 24 pumps.
And of course the climate in Israel or Tunisia can be compared to only some extremely southern regions of Italy and Spain.
Denser metropolitan areas have "district heating", which means water-transported heat that can be generated remotely by boilers, but there are also heat-pumps on these networks. For example, buildings can "sell" heat into the network with heat-pumps. Data centers do this.
Many buildings do not have a gas supply and many cities in Europe do not have metropolitan gas network at all.
Resistive loads are at best 100% efficient, your average heat pump is about 300% efficient.
Italy at least the southern parts of it and some other countries like Spain for example can probably transfer to a passive thermosolar water heating system like Israel uses.
TBH I’m not sure why it’s not more common around the world it’s cheap and fast it’s nothing more than a frame with some pipes in it covered by a pane of non-IR blocking glass.