The edit function is a great tool, but like many tools it can and has been mis-used. the mis-use is generally when someone is called out by Hivewatchers for not including source information, then they edit the post and tell people 'see I just don't understand what they think I did wrong'. it works for some but trying to view the original non-edited post is not an easy thing to do.
There were a couple people a couple years ago, who were going back to their old posts, editing them out and using the contents to make a new post. They were cropping photos to confuse the checks. They were caught.
Eventually most crooked people get caught, there will always be those that just do not care about that though and still return to their previous ways. A hazard of decentralization and anonymous accounts.