Because that's not how the prepositions worked in Latin. E.g. "Marcus ex casa exit" ("Marcus went out of the house") requires both the "ex" preposition and the "ex-" prefix in the verb. Heck, even today similar things can happen in English: "they gathered together", that sentence has two instances of "gather" in it.
Because that's not how the prepositions worked in Latin. E.g. "Marcus ex casa exit" ("Marcus went out of the house") requires both the "ex" preposition and the "ex-" prefix in the verb. Heck, even today similar things can happen in English: "they gathered together", that sentence has two instances of "gather" in it.