English nouns — other than those with natural gender, e.g. people or animals — do not generally have grammatical gender, and so are referred to as 'it' rather than 'he' or 'she'.
However, modern English has its roots in Norman French and Anglo-Saxon (Old English), both of which used grammatical gender for their nouns. In addition, other modern languages related to these continue to use grammatical gender today.
So, how come English doesn't?