A 28mm tire has roughly* 150% of the volume as a 23mm tire at the same air pressure, so you have more slack for how much air you can lose between rides (if you don't check tire pressure before every ride) and not increase your risk for either a pinch flat or actually denting the rim if you hit something hard and fast. The skinnier the tire the more it pays to be OCD about tire pressure (depending on how shady your riding conditions are, if everything is clean and flat then you have yet more slack around tire pressure)


* very roughly w/ simplifying assumptions for calculating volume of a torus...