It should certainly lower the bar of adopting a new codec if the implementation is in a memory-safe language.

Even so, it is more code, and somewhat more risk. Lack of safety elsewhere might end up using code that is otherwise safe in order to build an exploit (by sending it something invalid that breaks an invariant, or building gadgets out of it, etc.).

I can see that for components heavily interfacing with high surface area things like encryption, hardware interfacing etc., but why would that be true for a relatively “pure” computational problem like an image codec? Bytes in, bytes out.