“Sensitive skin” is a pseudo-medical term that is still looking for a definitive definition. As the authors say here…(bolded text for emphasis)
“However, as limitations, we would consider the
fact, that sensitive skin is defined mostly on the patients’
complaints and cannot be precisely confirmed by any
objective measurements. Furthermore, the definition is
rather general and, in fact, may cover different conditions
under the umbrella term of sensitive skin. Future studies
are needed to establish the specificity and sensitivity of
Basically, it is a term that many consumers use to describe all sorts of different conditions. These conditions don’t all have one solution. The products are formulated without things because that is what people who claim to have sensitive skin believe.
For example, people are told frequently that fragrance causes irritation. It isn’t true that all fragrances are bad for some people. Because fragrances don’t all contain the same chemicals. But marketers know consumers think this so they’ll call it out in marketing so people who believe they have “sensitive skin” will buy their product over one of their fragrance-containing competitors.
Similarly, not everyone with sensitive skin will react the same to every surfactant. So-called “gentle” surfactants like Glucosides were voted the allergen of the year in 2017. Surfactants that are less harsh to some people are more harsh to other people.
The bottom line is that selling products that are for “sensitive skin” is a marketing ploy. They aren’t actually helping people in the way they are implying.