Yes, it does fit rather formal occasions better. Or in written 'thank you' notes: "Jeg takker deg for hjelpen du ga min familie da..." (I thank your for the help you gave my family when..)

A more casual approach would be "takk" (as you suggested), or "takk skal du ha" (thank you, lit. *thanks shall you have)

Besides that, you could also see it as practise on how this word works. You can now say things like "Du må takker ham" to a child, for example.

Mostly used in formal writing and speeches.