Observation search query

Hi,
I want to try implement complex queries using FHIR Search https://www.hl7.org/fhir/search.html. The question is: why do some resources miss search parameters?
For example, in Observation page (https://www.hl7.org/fhir/observation.html#Observation) it is not possible to search by value integer or value boolean.
Another example, Condition has a very useful properties assessment, but no search parameters are defined for the reference.
Why is that?

Probably because no one has asked?

Probably because no one has asked?