Why are irregular verbs important?

There are around 180 irregular verbs in English . These are vastly outnumbered by the thousands of standard ones. 

The inflection pattern of regular verbs is so instinctive that young children and English language learners often regularize irregulars: I knowed that. 

Though only a tiny fraction of the verbs available, irregulars punch way above their weight. 70% of the verbs in everyday use are irregular.

So how have these tricky customers evolved? And why are they so central to English?