Eurovision, and gravity models

As the nation awaits tonight's Eurovision song contest, it's worth pointing out this paper (pdf) which proves what viewers have long known - that similar countries vote for each other; so Belgium and the Netherlands give each other high marks, as do the Baltic states.
This is part of a wider phenomenon - countries that are culturally similar, or geographically closer, trade with each other by much more than they should. Hence the success of gravity models (pdf) of international trade.
The puzzle is that, intuitively, you'd think that trade would be greatest between countries with the greatest cultural dissimilarities, because these have bigger differences in tastes. But the opposite is the case.