Why do some job descriptions emphasize object-oriented programming as opposed to procedural programming, scripting or other alternatives?
Inexperienced professionals who are new to object-oriented programming tend to use non-object-oriented techniques in programming that they are familiar with. Object-oriented programming is desirable for the following reasons: One, it allows code to be modular and reusable. Two, it allows code to be flexible and extensible. Three, object-oriented code is tied to compilation thus the execution in the CPU is faster. Scripts that are run through an interpreter are not as performance as binary code (compiled code such as .class files).
There is a legitimate need for some employers' to prefer candidates with object-oriented programming knowledge. For a basic example of object-oriented programming, see this posting. To learn more about object-oriented programming, you may want to read the Gang of Four book also known as Design Patterns: Elements of Reusable Object-Oriented Software.