Last names are irrelevant to those stories. Or the setting doesn't allow last names.
Last names are usually used in a story:
- To indicate that some characters are blood relatives (when there are no other means available).
- To differentiate between characters with similar first names, though nicknames could be used as well.
- When a need to use official-sounding language arises.
P.S. There's also a thing that first names are for family, friends and close acquaintances (person's informal environment) and last names are for a more official and professional environment (basically everyone else). So in some works we only see one side of the characters' social life, there is no context within the work to use the characters' other name(s).
Edited by Millership on Jul 20th 2018 at 2:40:46 PM
Spiral out, keep going.
Setting is also important. The Parrs from The Incredibles have an obvious family name, and so do the Robinsons from Meet the Robinsons. Those take close in sort of the modern era, when family names are pretty common. Mulan also has a last name, in a setting where family lines are pretty important. (I think her family is nobility of some sort, at least in the original story.)
Other vaguely placed stories in the past, not so much, which is at least partially in keeping with naming trends of the periods they were in.
In the name of being honest
A lot of real-life cultures don't have family names, either. Most Japanese family names, for instance, only date back to 1868-1870, when an edict by the new Meiji government required non-noble citizens to adopt one.
Echoing hymn of my fellow passerine | Art blog (under construction)
Either their full names are never revealed, or they LITERALLY have only one name. Most characters in Disney movies are only referred to by a single name.
What may be the reason behind this?