It depends. Sometimes it's better to encapsulate an expression in a function/method, even if it's only one line. If it's complicated to read or you need it in multiple places, then I consider it a good practice. In the long term it's easier to maintain, as you've introduced a single point of change and better readability.
However, sometimes it's just something you don't need. When the expression is easy to read anyway and/or just appears in one place, then don't wrap it.