In a lot of my engineering roles I have had to be internal/external facing and do things like budget presentations, work with partners, etc. Before that, I was a general web/app dev and we would get pulled along to client meetings all the time to collect spec, ensure that it was a good sales fit, etc. I'm not saying I had to be fully decked-out but being able to throw on a button down and tuck it in means that you "fit-in" to these situations.
For me, if someone is showing up in a t-shirt and jeans it's a red flag that you can't be bothered to dress semi-professionally which has been an occasional (but hard) requirement of me since day-1 of my career. 100% this all is anecdotal, and specific to my own needs/experiences.