I always carry flat fixing stuff (pump, spare tube, patches, tire levers) on every ride despite not having a single flat in nearly 5000km of riding this year. That stuff, plus a multitool, chain breaker, and spare chain quick link barely takes up any space so I don't see the point in leaving it behind. Everything but the pump goes in a single pocket of my trunk bag on my rear rack, and the pump mounts to the frame of my bike.