It'd probably be useful to understand the cultural and historical context... The fish isn't still alive just for entertainment or cruelty. The cuisine of this culture has always emphasized freshness of food, and that's what the live head is supposed to do. This is also a very old recipe, probably 800+ years at least. Obviously a recipe like this would not be developed in modern times.
Not defending this, as this is not ethical by today's standards, but to say "that's cruel" and believe it's isolated is biased. Production of foie gras isn't particularly animal friendly either, nor are factory farms.