I recall reading somewhere that the reason that these ESTA forms exist, or the travel cards for Britain and Australia is that if you arrive and they found that

I recall reading somewhere that the reason that these ESTA forms exist, or the travel cards for Britain and Australia is that if you arrive and they found that you really _had_ a criminal record when you ticked the box that said you didn't, is so they can throw you out of the country for providing false information on the document, rather than for having a criminal record.