In early March last year, before all Hell broke loose thanks to the virus, Garth was presented with the Library of Congress’ Gershwin Prize for Popular Song; the dress code, for at least the audience & presenters, is probably similar to that for The Kennedy Center Honors & the Kennedy Center’s Mark Twain Prize for American Humor (the first & third are taped for airing on PBS; the middle airs, on tape, on CBS). This is what Garth wore to the Gershwin Prize ceremony. So, yeah, staying true to his roots & I’m pretty sure the Joint Congressional Committee on Inaugural Ceremonies (aka JCCIC... Thank you, The West Wing!) understands that & looks the other way when it comes to dress codes for performers in the country music genre.
Look at it this way... it might’ve been Willie Nelson. Then you’d have gotten a scruffy-looking 80-something year-old man in jeans, boots, a t-shirt, possibly a bandana as a headband, with a badly beaten up guitar, extra hole from wear & tear included, & possibly/likely smelling of marijuana. And because he’s a legend, you wouldn’t have said a thing. Just like I’m sure probably happened with Garth.