We used to. Old English had all three PIE genders.

Very briefly, as our morphological case system was reduced, it became harder to distinguish between genders in words, more or less, all words were too similar for gender to matter. Eventually the definite article was reduced to invariable 'the' from an earlier paradigm of three forms, similar to German(the neuter form survives in a different function as 'that', however). The case system collapsed relatively quickly.

Other Germanic languages have also seen reductions in gender: a reduction to two genders, common or neuter, or total collapse, as with English and Afrikaans. Overall it's part of a Germanic-wide phenomenon of morphological marker weakening due to initial-syllable stress. Some languages, such as German, have developed in unique ways that allow them to keep the system, yet they still show a general trend towards losing the system.