LWaB and kerk have it right; Shimano pioneered inch-pitch "skip" teeth on 28T (14T) to 34T (17T) freewheel cogs in the early 1970s because customers couldn't be trained to downshift early and to ease up on the crank torque while changing gears.
__________________
"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069