Generally speaking for first impressions, it is always better to be over-dressed than under-dressed. Ultimately you as a candidate sitting in front of the interviewer(s) may come across better, and you might even feel more confident wearing something smarter than sitting in a t-shirt and flip-flops.
Saying that, it depends on the company and position. For example a consultancy, client-facing, or management positions will potentially expect you to be more presentable. It's perfectly fine to enquire what the culture is like in terms of dress if you aren't sure and you can act accordingly (perhaps what their normal is but a tiny bit smarter). For example, my last interview was for a smaller start-up sized consultancy and I was told by their recruitment to dress casual as for that sort of company culture mattered a lot (I also had an hour long 'cultural fit' interview). This doesn't mean to say that you won't get the job for dressing too smart in this sort of situation, but the companies criteria could be anything.
It's a difficult balance and it will vary from company to company. If ever you're in doubt and it's still unclear after some investigating, it will hurt your chances less to dress smarter than it will to dress casual.