This is related to bug 51293 and the general bug 38129:
The alignment options in the media dialog's advanced settings are:
These are the four explicit settings provided in MediaWiki.
Most users, even if they click on a few buttons to consider other options, are going to want the image at the default (i.e., on the right for left-to-right languages). It is the convention to not specify the default, mostly to avoid needless clutter in the wikitext.
Most users have no idea what "None" does because they've never encountered it before. They're going to think that it means "unspecified default", rather than left-and-clear.
It would be good to offer a "default" button, even though this duplicates the function of one of the existing buttons.