> "fertility awareness" (on its own) is a less reliable means of contraception than most other options
You're absolutely correct, of course - but some people's situations don't require such a high level of reliability. For instance, my wife and I used the rhythm method for four years after marriage without incident, until we decided to try for our first child.
During that time an unexpected pregnancy would not have been unwelcome. We weren't where we wanted to be financially, but we would have been fine. Our ballpark assumption of a 10% chance of conception per year was an acceptable level of risk to outweigh the negatives of a barrier method or hormone-based option.
If you only rely on this method for a few days each month immediately after the end of menses, the chances of it failing are MUCH lower than if you rely on it for a week prior and a week after menses.
That said, wiki claims[1] that the latter approach is >95% effective in perfect use, and 88% effective in typical use.
Compare this to withdrawal[2], which wiki claims is 96%/78% effective respectively.
[1]: https://en.wikipedia.org/wiki/Calendar-based_contraceptive_m...