I’m no developer. Consequently, this is personal opinion
Built-in style names do not describe the visual effect of their application. They were given names emphasising the semantic value attributed by an author. This is valid for all style categories except perhaps list styles.
Styles primary role is to mark up your text with semantic significance. Typographical attributes come last. And since these attributes are rather limited in number, several distinct styles may end up with the same visual appearance but must remain separate for ease of document tuning and maintenance.
Among character styles, you have Emphasis not “Italics”, Strong Emphasis not “Bold” or Source Text, Teletype and User Entry all three giving a monospaced font but covering three different variants.
“Subscript” and “Superscript” may be too close to the visual effect (though I admit it might also be a semantic value in some cases). Taking the example of “Superscript”, this could cover power factor (in math formula), upper index (in some chemical notations or tensor analysis), operator, … They all need to be distinguished by a different style so that you can format them separately.
Note that these usages pertain to technical domains while built-in out-of-factory style names cover common rather “literary” documents like letters, notes, dissertations, novel, …
The way to avoid to define over and over again your “Subscript” and “Superscript” character styles is to store them into your personal template and make this template your default.