Field default only applies to registrations and only if the field is displayed on registration. There isn't a way to set a default outside that scenario. For profile edit I recommend just marking the field as required so they have to select a value. To ensure some sort of default you'd need to use CB Auto Actions and a Field action, but where you enforce it would be up to you (e.g. could be after registration if you don't want the field displayed on registration). As for imports you should be able to just specify the value in your CSV import file.