XLOOKUP lets you specify what should happen when a match is missing. That small design choice affects reporting, charts and later calculations.
Blank output
An empty string can make a report look clean, but it is still text. Downstream calculations may treat it differently from a truly empty cell.
Zero output
Returning zero is useful when a missing item should genuinely contribute nothing to a total. It is misleading when “missing” and “zero” mean different things.
Visible message
A label such as “Not found” is best when a human needs to investigate missing master data. It makes data-quality problems visible instead of silently masking them.
Choose based on the next step
Design the fallback for the consumer of the result: a chart, another formula, an export or a person reviewing exceptions.