> We won't go poking through waste disposal sites for no good reason
We don't need a global collapse to make disposal sites problematic. Imagine the total dissolution--think post-Ghadaffi Libya or Iraq and Syria at the height of ISIL's power--of a state containing nuclear waste. Keeping nearby civilians, who could have forgotten or never known of the hazard, from harm seems like a good enough reason to give this some thought. (I agree with your general sentiment, however.)
That's similar to how I approach the original problem - if human knowledge has regressed to the point where we don't know where radioactive waste is stored nor how to recognise it, there are probably countless other problems, and hazards they we haven't considered. It's an interesting discussion in theory, but I'm unsure how important it is in practice.
Perhaps more relevant are the accidents in Tamiku (Estonia), and Lia Lilo (Georgia), that followed shortly after the dissolution of the USSR and involve the inappropriate handling or complete abandonment of radioactive sources:
Having never heard of this event before, the fact that this has been called one of the worst nuclear events, speaks to just how tightly nuclear waste from energy production is regulated, in my opinion.
Living on top of granite at altitude is a fairly good yardstick for radiation exposure comparison / risk evaluation, as far as the layperson's (that's me!) understanding goes.
We don't need a global collapse to make disposal sites problematic. Imagine the total dissolution--think post-Ghadaffi Libya or Iraq and Syria at the height of ISIL's power--of a state containing nuclear waste. Keeping nearby civilians, who could have forgotten or never known of the hazard, from harm seems like a good enough reason to give this some thought. (I agree with your general sentiment, however.)