My hunch is that brands are pushing wider tires because the average customer isn't the light, young racing type.
If you're reasonably light - 65 to 75kg - and want comfort, you can simply ride 23s or 25s at less pressure. At 90 psi they offer a much more muted ride and I found myself even faster on bad roads with around 80 psi.
But for the average customer, 28mm tires may be needed to be able to use comfortable pressures.