Originally Posted by
Redbullet
Many of us still make relatively short rides (60-80 km) on reasonable quality roads where 25 mm tires (or sometimes even 23 mm) would marginally harm (or not harm at all) the ride quality, but they perform a little better. In such cases, it would be nonsense to switch to wider tires with associated penalties in weight and aerodynamics, for a comfort that remains theoretical.
Pros can often take advantages from switching to wider tires because they make much longer rides, on variable quality roads, and their bikes (including wheels) compensate for weight and aerodynamic losses by much more expensive setups that are not reachable by casual riders. I think that the general "necessity' of going wider to 28-32 mm does not exist; it is valid only for specific riding conditions.
Unless you are obsessed with marginal performance gains on the smoothest of roads then the benefits of slightly wider, lower pressure tyres are pretty obvious for most riders. Especially on the endurance road bikes that are often fitted with 32 mm tyres eg Trek Domane or Giant Defy. Those bikes are by definition intended for longer rides on variable quality roads. It wouldn’t make any sense to fit those bikes with 23 or 25 mm tyres, which is why they don’t.