Switzerland is very conservative, I'm not all that surprised if it didn't pass.
Prostitution is legal, abortion is legal, and they have pilot trials for "cannabis clubs"
And then you look at the actual rules (https://en.wikipedia.org/wiki/Popular_initiative_(Switzerlan...): "A double majority of people and cantons is required to change the constitution."
--> Swiss cantons are split up historically, not by population, similar to US states. The conservative, low-pop cantons can hold the progressives hostage on anything they don't like because even if you get the liberal cities behind you that is still way beyond the majority of cantons.