Il distingue deux types d'options: the ones the user can not change and the one he can specify in their parameter.

An important example of default option is the organ donation : countries that make habitants donors by default have a great way to supply the health system. The ones that doesn't want to give their organs can be registered to a list.
On the contrary, less people are donor if it is not done by default. France has changed it in 2016 and the donations have rised.

About digital systems:
If a user accepts notifications, does he have to get them all ?