Here's why:
* Different cultures have different sign languages. Just like spoken languages, sign languages vary widely across different countries and regions. For example, American Sign Language (ASL) is distinct from British Sign Language (BSL), French Sign Language (LSF), and many others.
* Sign languages are not simply visual translations of spoken languages. They have their own unique grammar, syntax, and vocabulary.
* Sign language learners need to be exposed to and learn a specific sign language. You can't just use the same hand gestures to communicate in different sign languages.
It's important to understand the diversity of sign languages and to respect their individual identities. While there might be some overlap in basic signs for common concepts like "eat" or "drink", the overall structure and meaning of signs differ greatly between languages.