People run those common places thousands of times and occasionally still not getting anything of value.
Drop rates are just so damn tiny for, say, a Ber rune that you have mostly luck and continuinity to rely on. In theory, I can promise you it will drop. In practice, I played Diablo 2 since 2003 and only slowed down in 2018, done 99 once and 98 some 10x and I haven't found several items not even once - looking at you, Griffon's Eye.
Cryptography
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