Imagine if there were a way to set up a new notificant record from right on the Tribute page - a shortcut to add just the most relevant information like:
First and Last Name
Contact info (likely address or email)
Constituent status (if you don't want to treat notificants as active constituents)
It makes more sense to be able to create a notificant in a tribute than adding them as a constituent first. They may never have a relationship with the organization, so no need to add them to your constituent totals.