As with any invisible or otherwise difficult to monitor birth control method, this is really only for people in dedicated relationships.
It goes both ways. A man shouldn't trust a women he just met to be on birth control. A women should have the same reservations.
This is for people who can trust a long term partner, and who wouldn't be destroyed by the failure of the product. And that's still a huge market.
You could feasibly fit it into the actual lore and make it "balanced" in a sense. The party finds a relic with the power to rewind time by a few moments. Becomes inert for a few days/play sessions after use.
Then there is actually the potential for complete failure (the relic holder dies instantly before being able to activate it), but they still get a sense of safety that propels them into stupid dangerous stuff all the time.