I am afraid it is nothing more exciting than the fact the person giving the census taker the information did not know where the person was born.
It could be because the person was a 'boarder' or maybe a neighbor gave the information.
Why someone is missing from a census has been addressed previously. Also bear in mind the online census indexes are not perfect. I have many hard copies of censuses from the National Archives where I cannot find the people online. Sometimes one can figure out the problem such as faded ink, wrong name but other times there is no reason the person is not listed online. Of course some people were just missed; some were counted twice.
I would say 'loafer' etc. were given probably by family members or neighbors who did not have the highest regard for the person.
Census records are not the best of 'primary source' documents. They do not list who gave the information as death records do. Death records are also not the greatest. Birth and marriage records are probably the best primary source records. Wills and Deeds are legal documents which are very valuable as people are getting 'money.'