Who said languages were only ever or the other?

All languages have some notion of static types and dynamic types. They're most easily bucketed by whether they consider more than one type.

C is statically multityped but dynamically unityped. Python is statically unityped but dynamically multityped. Haskell, since it uses lazy evaluation, is statically multityped and dynamically multityped.

The main issue with static unityping is that insufficient testing can easily lead to type errors in production (or worse). And static multitypes help static analysis tools reason about code more easily.

Introducing a new type that is intended for use in a specific context that can easily be tracked is tremendously useful when programming at scale.