Why we use DLL

1. We can hide some "static" code from users as they have no need to modify it and pay attention to it. Anyway, you can extend basic classes to add new specific features to them.
2. We can reduce source code compilation time with DLL.
3. We can protect out copyright in this way. Unfortunately, Unity doesn't care about source code copyright violation and we had problems with attemts to copy our asset by other developers.