The picture you linked to is taken in A Coruña whose mean temperature is around 10 degrees higher[1] still than relatively mild[2] climates near the arctic circle.
I didn't mean to suggest they weren't also used to let light in. I've spent a lot of time in houses that have these installed, letting light throughout the day while keeping the house relatively cool is a constant balancing act. I meant that without the need for the thermal management you'd go for other sorts of systems, such as internal blinds.
I.e. I'd expect that in places like A Coruña you'd use these for thermal management in the summer with the outer windows open, whereas in Iceland there's maybe 1-3 days of the year where the outside temperature is anywhere near the inside temperature.
In most of Spain they are installed outside of the window glass, but in the north they are installed inside, so they are protected from cold and wind. As in this picture, for example (just found at random): https://www.inmoatuel.com/piso-exterior-de-90m2-reformado-a-...
But they still seal the window hole perfectly so they block light much better than blackout curtains. I suppose the problem with Monachil is that it's a cold place, but within Andalucía which is generally warm, so they don't have a tradition in the area of installing blinds inside as is the case, for example, in Galicia, where you can definitely see them even at high altitudes where snow is common.
When I go on a camping trip... indeed I just don't sleep well, I'm afraid :)