Reading and Writing in the Deaf community

Hi folks, I hope this is an okay place to post this, if it isn't I am sorry!

I ran into something today that struck my curiosity, and I am eager to learn more.

I was at Vancouver International Airport earlier today going through customs. They have a large board with "Welcome to Canada" written on it, and a few simple instructions. The message is written in about 12 different languages. In addition to the written languages, there is also a video on the corner of a man signing the message in ASL.

It just got me wondering as to what the purpose of this is. I fully understand that ASL is a language all on its own just like any other, but I also thought that the vast majority of those fluent in ASL would also read and write in another language more suitable for written communication.

I understand that for many, ASL is their primary language, so my initial thought was that they included ASL on the sign not so much as a matter of practicality, but, rightfully, as sign of inclusivity and welcomeness.

I'm sorry if this question comes off as ignorant, I just was very curious and want to understand more. Regardless, it was great to see so many languages welcoming everyone to Canada!