Unless you have a radio failure or there just is nobody to operate the radio at a small strip.
You are identing a beacon
You want a really basic approach aid that requires minimal infrastructure on the ground.
Or like anachronistic ways of doing sums.
The whizz-wheel is anachronistic, but it does work. Using it does no harm and does help somebody develop an intuitive feel for what all the numbers mean which putting it into an electronic device doesn't so well.
I don't use my whizz-wheel much, but it's there and occasionally is handy. NDB approaches and signal squares on the other hand are certainly a regular feature of my life (albeit probably not in the same aeroplane at the same time!).
G