Even though tech / "IT" people are usually casual, I think it doesn't hurt at all to show that you take the even seriously, and that you own a suit and are not afraid of wearing it if some particular client meeting / other event ever necessitates it.
If they are wearing a suit, how familiar with the industry are they?
That's also ignoring that suits are the uniform of finance, politicians, sales, and business. I view suits in the business context as nearly synonymous with corruption. A suit is like a giant billboard saying "I am/want to be corporate," "I want to increase shareholder value," "I only care about next quarters profits," "I want to participate in the dominance hierarchy."
FWIW, cultures are very different. On the west coast dark jeans and a collared shirt is being dressed to the nines (hyperbole). I'm led to believe that suits are kind of an east coast thing.
When reading these answers, I would be very careful about understanding that the answers are a function of the answerer's culture. This question is likely to have wildly different answers between the west coast, east coast, India, japan, Europe, etc. Even the companies themselves have dominant cultures. If you're interviewing for Bloomberg, you should probably wear a suit. If you're interviewing with a company that isn't a tech company, you should probably wear a suit. If you're interviewing in the valley, a suit probably isn't the right choice.
Also if it's very clear you are from a different culture (having any kind of accent), I think wearing a suit would be seen as you being from a different culture and greatly discounted as a meaningful signal than if you are from the same culture (no accent) and wear a suit, which means you understand what the suit represents in the culture that is judging you.
At the end of the day, if you nail your technical questions, it won't matter.
It's more important that you 1) look tidy and 2) are comfortable and 3) match the style of the workspace to a degree.
You might just wear it to look good, but there might also be this unconscious bias that you're using money to compensate for something.
To neutralise the look, one of my friends wears a Simpsons tie, which suggests he's wearing the suit because he wants to, not for any other purpose.
The blazer may come off as the meeting starts.
And if you speak and interact well, there is no chance they'll misunderstand being well dressed for lack of confidence.
A well-fitting tailored suit would make you look sophisticated, but if you’re wearing a crappy off the rack Kohls suit that’s all baggy and stuff, you’re just gonna look like a goof.