What Language?

I fail to understand why every time I enter into Scrivener I have to specify what language I’m writing in. I have a default language set in my MAC but I write in three. So when I create a document on scrivener that is not written on the default language of my MAC, every time I open the document I have to go to Spelling and Grammar > Show Spelling and Grammar and then specify the language. Would not be a lot easier to be able to specify a language in which the document is written? I haven’t found that option. I would expect to find it under File - Properties, but there is not even an option to define properties of the file. :confused: