SUVs generally have tall cabins, but lack in horizontal boot space and depth. The floor plan of the car matters a lot. The main selling point of big estate cars (Volvo V90, E-Class T-Modell, Skoda Superb) is the rectangular shape of the boot, coupled with a flat floor with the seats down. The metal loading lip is also at the level of the floor, making access easy. Some also have additional storage compartments under the boot floor, and even specially designed extra-size fuel tanks.

Ah true, but as someone that might buy a (used) car in the next few years: trendiness & freshness do play into this as estate cars do lose points in my book for their "old-school" look as it was the type of car people had when I was a kid (and I am nearly 40).

So that together with the higher ride height, which makes getting kids in and out easier and almost no extra cost makes the SUV more likely to win than a similarly specced estate.

(and please keep in mind a "SUV" in Europe is not really the same as "SUV" in the states).