Because the new policy is not about tourists (though they are collateral damage in this) but rather a focus on the local situation since the Swiss vaccination picture is quite poor compared to the rest of the EU and even to the US. This is being done to “force” more Swiss to vaccinate; it’s the same approach as what France did originally with the Pass Sanitaire; there you could enter the country with your CDC card but then you would be SOL in terms of visitor attractions and indoor dining etc without the QR code. But this being Switzerland, establishments will likely be more “obedient” in following the law than lots of places in France…