Why is std::hash not guaranteed to be deterministic?

Question

Hereafter, we use N4140 (C++14 Standard).

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According to § 17.6.3.4 Hash requirements,

The value returned shall depend only on t

Answer 1

This answer (and links in it) suggested by @NathanOliver is ultimately helpful. Let me cite important parts.

For a non-cryptographic hash function, it's possible to pre-calculate massive inputs with the same hashed value to algorithmically slow down the unordered containers, and results in a denial-of-service attack.

(from Issue 2291. std::hash is vulnerable to collision DoS attack)

For this reason, language designers are migrating to random hashing. In random hashing, the hash value of the string “a” can change every time you run your program. Random hashing is now the default in Python (as of version 3.3), Ruby (as of version 1.9) and Perl (as of version 5.18).

(from Do you realize that you are using random hashing?)

Move to Ready, rather than Immediate, as even the permission has been contentious in reflector discussion

(from Issue 2291. std::hash is vulnerable to collision DoS attack)

In practice, as far as I understand, no implementation of std::hash implements random hashing but you can write your own my::secure_hash.

(from this answer)

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P.S.

I just googled "hash table dos" and found an informative page: The moment when you realize every server in the world is vulnerable.