Zettelkasten promotes reuse
Zettelkasten notes are atomic. It is this property that allows for very concise, accurate linking between notes and concepts.
Larger arguments are often built up by linking together many of these atomic notes. Instead of explaining a concept inline, a simple reference is made to one (or more) notes which contain more detail.
This avoids repeating the same information in multiple places and encourages the formation of a densely linked web of notes.