the widespread use of carbon rims has helped negate the added weight of larger tires. Even Paris-Roubaix is exclusively run on carbon rims. I don't think anyone this year will run metal rims. Maybe one or two riders
In the classics, it's obviously better for wider tubulars where lower psi and pave are the norm. Better comfort and less chance of flatting.
25's are becoming more widespread because of the shape of the contact patch. There is a compromise between comfort/flatting/rolling resistance/weight/handling with 25s that is acceptable for racing.
It's also the trend now, and that trend may change with the wind.