Because there are snow leopards living in the Pamir Mountains? Perhaps you're the one who needs to do more research
If you did your research you would see people spend thousands of dollars and weeks going deep into the mountains trying to see snow leopards and don't manage it! Your odds of even seeing one anywhere near the Pamir highway, let alone getting attacked, is close to zero. In fact I don't think there is a single recorded case of a snow leopard attacking a human anywhere in the world.
Also, in 2018, is crossing the Afghan border to visit Ishkashim without obtaining an Afghan VISA still allowed?
If you did your research it has never been possible to cross into Afghanistan without a visa. You can visit the market but it's not in Afghanistan, it's on an island between Tajikistan and Afghanistan (I think technically Tajik land or maybe no-mans land, but definitely not Afghanistan.