Looking at Stack Exchange websites, there are some answers with many down votes like this one (just an example).
For what reasons for don't we delete / remove these kinds of answers?
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Why should all downvoted answers be deleted?
A wrong answer, downvoted, also conveys information. It tells you, the visitor: don't do this. This answer is wrong, and if you are lucky the comments tell you why it is wrong.
If we deleted such answers, someone else might make the same mistake.
So instead, we (try to) only delete answers that are not answers (when they are new questions, or comments, or gibberish), or spam, or offensive, etc. We don't delete answers merely because they are incorrect.
Not all the downvoted answers are deleted. There is a reason to delete an answer, if it is:
not an answer (it was posted as an answer, but should be a comment or edit, or something else (e.g. What things did you use and why didn't it work?) )
link-only answer (because information, accessible from the link can become invalid due to server fault, etc)
very low quality (and cannot be improved by editing)
it is spam (simply advertisement, promotion)
If it does provide an answer, even incorrect, it won't be deleted (unless it is full nonsense).