Object-oriented developers look at ways to reduce the cost of creating objects – especially when those objects are expensive to create because they require, for example, a database pull or complex mathematical operations. Another reason to invest in reducing the creation cost of a particular object is when you create a lot of them. Nowadays, backend developers tend to disregard this aspect of optimization as on-demand CPU/memory have become cheap and easy to adjust. It'll literally cost you a few bucks more a month to have an additional core or 256 MB of RAM on your backend.
This used to be a big deal for desktop application developers too. On a client desktop, there is no way to add CPU/RAM on demand, but fairly cadenced quad cores and a ridiculous amount of RAM for a consumer PC made the issue less problematic. Nowadays, only games...