Other Countries
Abdication is more common in other countries. In Japan, there are more emperors who abdicated than died in office. Empresses often surrendered the throne if a more suitable man was present. Fairly recently, King Juan Carlos of Spain chose to give up his position for Felipe. His son was crowned in 2014.
Old Age
It is something of a norm in the Netherlands as well. Three queens have consequently abdicated for their heirs! In other countries, monarchs resigned because of old age. In the past century, places like Bhutan, Belgium, and Qatar have changed sovereigns for this reason.