According to the [discussion at that time][1] the main reason is that you cannot contact the user who deleted/modified your work while having anonymous edits. Also, there might be a licensing issue. Of course you cannot identify registered users but it is still possible to keep track of all his their edits under this the same account. [1]: http://lists.openstreetmap.org/pipermail/talk/2007-October/018853.html

According to the [discussion at that time][1] the main reason is that you cannot contact the user who deleted/modified your work while having anonymous edits. Also, there might be a licensing issue. Of course you cannot identify registered users but it is still possible to keep track of all his edits under this account. [1]: http://lists.openstreetmap.org/pipermail/talk/2007-October/018853.html