All sorts of hash functions expect 64-bit intermediate values. Worse, these algorithms are liable to go haywire, and return very-not-randomized results if intermediate values are silently truncated to 56 bits (or magically become floating-point and thus lose their lower-order one bits) as happens when they're naively translated from C to JS.
As a pure quantity representing a real-world value, probably not very often, but just as a series of bits or a more abstract quantity like a memory address, it will often go above 2^56. Many algorithms and binary file encodings use 64 bit integers so interfacing with them in Javascript is hard.