That assumption is predicated first on the idea that people can and will tell you their likelihood to recommend within a reasonable degree of accuracy. I don't think they do.
1: https://www.xminstitute.com/data-snippets/gap-consumer-recom... 2: https://hbr.org/2019/10/where-net-promoter-score-goes-wrong
> If you believe in that core assumption that NPS measures word of mouth, then this interpretation of "likely to snag some other customers on my way out the door" is a sensible one.
But that's not the scale given to the respondent. The scale is given as going from "not at all likely" to "very likely" to recommend. There isn't an option for likely to recommend against. The low end of the scale probably captures some, but to assume it is near 100% is a mistake.