[bretthopper]

The one caveat this article doesn't mention is worse handling but they replied in the comments about it. And handling matters way more at higher speeds, plus they commented the extra weight matters more for steep climbs too.

[Cockbrand]

This, and a wider tire also has a larger front surface, resulting in more aerodynamic resistance. As every watt counts in the pro peloton, this is an important factor. For us amateur riders, probably not so much.

[loeg]

I was a little surprised: the weight difference isn't huge. It is about +27% between Conti 5k 25mm and 32mm, or 60 grams per tire.

Aerodynamics are the only real reason, I think.