Familiarity is a huge factor in decision-making. Apple, a multi-billion dollar company, made the Apple Watch to track your health. Something was missing for half of the population: cycle tracking. No decision maker was familiar enough with women's health to understand the importance of aligning cycle information with other health information.
People keep repeating this story, but is there any real evidence to support that this was actually an oversight, and not a deliberate decision? Apple has a long history of making decisions that seem to go against what users want, like removing the headphone jack, and making a wireless mouse that can't be used while charging. Both of these decisions were made deliberately and intentionally. For the headphone jack, it…
That might have been one of the goals but I doubt it was the only goal. Another reason for removing the headphone jack is dust and moisture ingress protection. It's difficult to achieve an IP67 rating in a phone with a 3.5mm TRS jack. This is due to the shape of the connector and the extra thickness you need to add to accommodate a jack with sealing rings. By switching to the lightning connector exclusively, Apple was able to achieve IP67 ratings in all their phones after the change.
This is a huge improvement for users because previously a lot of phones were being brought in for service showing liquid damage. Having your phone die due to dropping it in some water is a terrible experience that is now quite rare due to the IP67/IP68 ratings of modern phones.