Because canon wise they don't use Romanian names for anything. It wasn't until the 3rd ed.
Gazetteer I that Balok was compared to Romanian anyway, and even then, they still used the same names for places that were in the old 1st ed. and 2nd ed. products. We did give some streets and back alleys in Vallaki Romanian names.
(also, nobody on the dev team speaks a word of Romanian, whereas EO, who designed Dementlieu, is French-Canadian and speaks French fluently
)
Back to Dementlieu, I'd rather that French only be used for proper names (names of people, names of places) and not for every darn thing under the sun ("we don't sell 'swords,' we only sell 'épées!'").