We generally only put the examples where they add something substantive.  Otherwise, it just make the docs verbose and time consuming to read start to finish.

Adding an example for str.lower() contributes no additional value.  Most published Python books would all avoid the unnecessary here as well.  FWIW, we have no evidence that any user has ever found the current form hard to use.

So, let's close this.  If you're looking for places to contribute, please look at the open bugs where there are known problems.