Why do people persist in mispronunciations and misspellings when they have had numerous examples of proper usage?

Examples: My patient who repeatedly referred to his prostate gland as a "prostrate gland". He had heard me say it properly many times.

A user here who insists on spelling borders as "boarders" although he has had many examples of correct spellings of this word.

What is up with this?


Why do people persist in mispronunciations and misspellings when they have had numerous examples of proper usage?
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