We do have both tuples and functions with multiple arguments. But nobody considers supporting both a wart. It is a similar case with named/optional arguments and structural records.
Rust treats arguments differently in many ways: (a) lifetime elision, (b) reborrowing, (c) impl traits, and I am sure others (I am no means a compiler expert). At least (b) and possibly (a) should be different between arguments and structs. That is why IMO it is a mistake to conflate the two.