As fun general rules of thumb:

Hard 8 character limits are often a side-effect of old COBOL "databases" in the backend somewhere.

Hard 16 character limits are sometimes a side-effect of old versions of Active Directory in the backend somewhere or new versions of Active Directory in certain backward compatibility operation modes/certain group policies.

Hard character limits in general are often a sign that someone is storing the plaintext somewhere they shouldn't be.

(Soft character limits today are mostly to avoid possible hash function DDoS.)

The 14 character password limit in some versions of Windows is a side effect of using LM and NTLM (original "flavor", not NTLMv2) hashes used in Windows NT domains and maintaining compatibility therewith. It's not related to Active Directory, per se.

Nobody should be using LM or NTLM hashes anymore today, for all that that means... >sigh<

It's so you can enter your password over a touch-tone phone.

Shared credentials with phone or ATM banking.