It's about dryness and high attenuation. Low mash temperature (148 F) and a little sugar addition can help. However, many/most of the Belgian yeasts are high attenuators anyway. So to the American palate, the low mash temperature and sugar are possibly optional, unless you like your beers quite dry indeed. Part of it is personal preference. The Belgians just really don't like sweetish low attenuated beers, in general, so they take measures to avoid this. The American palate probably doesn't care nearly as much.