The fact that we still do things that are not necessary for survival per se shows that it’s built in. That said, ‘ritual purpose’ is a lazy way to describe odd items that get dug up.
“shows that it’s built in”
There certainly isn’t any obvious survival purpose to the cave paintings, or any other ancient art. We kind of assume “ritual” is involved because people assembled in larger groups than their normal living-group size.
In the case of the dagger, it’s fancier than strict practicality calls for. That could just as easily be for status as for ritual, “I’ve got a fancier knife than my cousin has!”