What is the motivation behind Key-policy Attribute-based Encryption? What is Attribute Based Encryption? has a nice explanation what both forms (Ciphertext-policy Attribute-based Encryption and Key-policy Attribute-based Encryption) are. 

My question is: what is the motivation/analogy behind Key-policy Attribute-based Encryption?

CPABE can be regarded as a variant of Attribute-based Access Control (ABAC) which is a well understood technique. What would be the KPABE equivalent, if there is one?

My take for an example key policy 

$$(\text{Student}\wedge\text{Course}_A)\vee\text{Staff}$$

would be that $\text{Student}\wedge\text{Course}_A$ and $\text{Staff}$ can be seen as roles (RBAC) which will be activated through the attributes in the ciphertext. Is this an accurate analogy? Can you come up with a better one?
I believe the answer cygnusv gave is not fully correct. If an object is tagged with "NUCLEAR, TOPSECRET" it can potentially be decrypted by someone not having the TOPSECRET attribute (or NUCLEAR attribute). Why? Because it all depends on the structure of the private keys in the system. 

A private key could for example be: "NUCLEAR or SCIENCE LAB A". Thus it would suffice for the object to be tagged with NUCLEAR for this person to gain access.

This is also one of the reasons to why KP-ABE is "less intuitive" because the encryptor does not specify the relation between the attributes that are tagged. Instead it is the key authority (or just authority) which will decide how these attributes needs to be combined for access.