Why can a sentence begin with a contraction but not end with one?

A sentence can begin with a contraction because contractions serve to combine two Words into a shorter form, which can function as the subject or the beginning of a clause. However, ending a sentence with a contraction can lead to ambiguity or confusion about the sentence's meaning. For clarity and formality, it's generally preferred to avoid ending sentences with contractions, although it may occur in informal contexts.