Segments are useless.
1. Customers are continuous, not discrete
In any customer base, customer purchases are a spectrum. In fashion, for example, the first segment used is often gender, but shoppers buy clothing for themselves and their spouse. In pet food, dog households sometimes get a cat, and it can take months to get resegmented.
How you think your customers behave...
... versus how they actually are
2. Segments are hard to target
Beyond email campaigns, it's hard to action any given segment with broad reach, promotions, or price advertising.
3. Why be right-ish when you could be right?
It's often just as easy to use the underlying raw attributes instead of the segments. So rather than talk to the "Healthy Nutrition Mom" segment, why not just choose anyone who has bought organics in the past few purchases? It's more complete, and doesn't rely on shaky correlations of other factors?