The issue is how someone cares for their personal appearance. You say that other people dress down; sure they do! What if all the the successful software engineers wore only their underwear?
Well, they are, on top, anyway. Hence, this thread.
Earlier I made the comment that dress revealed the respect that you had for your audience. When I do public appearances, which I do, I dress properly. Next month will be a coat and tie appearance to a group of about four hundred people. Am I wrong for dressing up for my audience? Or, should I tell them to stick it; I’m dressing how I want to because my ego demands you accept me as I am?
Tell me, would you think any less of a person who dressed in a nice shirt, possibly with a tie? Or, does the T-shirt thing get your gears turning?
If you’re good enough, your audience won’t care how dress. They’ll even consider it a sign of your excellence.
If your’re not that good (not a put down, just reality for most of us), you’ll have to dress up.