Gear oils in motorcycles work very hard for their living.  The pressure between helical gear teeth calls for extreme film strength under demanding conditions.  At the same time, the oils need to offer very low drag, minimal foaming and very often have to let the friction plates in wet clutches grip.  In shaft drive bikes, the final drive has to deal with even more pressure, especially under accelleration and heavy loading.  Careful selection of your bike's transmission fluids can pay dividends in terms of performance, reliability and longevity.