As the parent comment said, he stood out for dressing nicely those years ago. Wearing jeans in the 2000s was not just tolerated or accepted, it was expected. I remember feeling wary of engineers who dressed up for interviews then, like they were trying too hard.
Very much my impression too. I work for an org with sites scattered across the country. My colleagues in Virginia still regularly wear suits, while I in California haven't even owned a suit in many years. For no particular reason I can discern, the gradient seems to be pretty linear. Our Texas people are right in the middle formality wise.
It entirely depends on the industry. Banks, government, defense, etc. will feel very stuffy even on the west coast, while web companies will have greasy unshaven slobs even in Manhattan.
My general belief for interviews is to dress one step up from what you'd be wearing on a day-to-day basis at that job.
I wear shorts and a t-shirt (often a DEFCON or BSidesPDX shirt) usually, so I'd wear jeans and a solid color t-shirt or possibly a polo to an interview, though I haven't done an in-person interview for a job since 2016. For remote interviews, I'm in sweatpants and a polo.
In the early 2000s, I wasn't a tech worker yet, but I always assumed engineers were wearing khakis and a polo, so I would have shown up to an interview with black slacks and a button-up shirt, maybe even a tie.