It's pretty big when you take into account whole context. Stuck up "socks size is a rule" UCI, historical norms, technical limitations (25mm is a limit for caliper brakes), tire tech (wider tires used to be heavy)....
My prediction is 27mm being the norm in next 5 years.
Currently I'm riding a decade-old road bike. It was fancy at the time because it fit 25mm tires without issues. People would give me shit for "slow" tires on group rides. But 25mm tyres improved a lot in that time. Now I wish it could take 27mm :(