I'm not convinced this is true. A simple grammar can express a whole lot of information. I think complex grammar is desirable in some cases because a lot of way

I'm not convinced this is true. A simple grammar can express a whole lot of information. I think complex grammar is desirable in some cases because a lot of ways we choose to make grammar more complex are ergonomic. Binary infix operators, various kinds of brackets and braces, ... it all is a bit more difficult to describe as a grammar, sometimes more difficult to learn, but also closer to natural ad-hoc ways that technical people would write things down to communicate them. Just see the typical ways of writing mathematics as an extreme example.