The gear ratio is the number of turns of the engine crank shaft (input to the gear set) per turn of the gear set output shaft which drives the chain (obviously on chain not shaft drive bikes). What difference the ratios make also depends on the ratio of the front sprocket teeth to rear sprocket teeth and size of the rear tire. What it all amounts to is engine speed vs. bike speed (or engine revolutions per mile) in each gear.
IMHO none of this matters to most riders except racers or those who intend to do drive train mods. I don't know of anyone who bought a particular bike because of its gear ratios. The numbers are easy for the manufacturers to determine and don't give away any secrets, so they publish them. Now, how about publishing rear wheel horsepower?