Why does production and test environments need to be similar?

A test environment is where the testing teams analyze the quality of application. This also allows computer programmers to identify and fix any bugs that may impact smooth functioning of the application or impair user experience whereas a production environment is where the latest versions of software, products are pushed live to the intended users. 

Having a production environment similar to testing environment is essential. This is to ensure the end products in live environment to be quality and bug-free same as testing environment.  

As show in the picture, the production release has the same version as testing environment. In other words, the production version is well tested.