Why does Solidworks allow you to change the gear ratio?

[colin4953]

i am new to SW and i was doing a tutorial on gearmates.
when you mate 2 gears SW determines the ratio based on the 2 sizes right? why does SW allow you to change the ratio without changing the gear sizes? when would you ever need to do this? also why do my gears always run into eachother? see pics

http://farm4.static.flickr.com/3058/2288927501_97edeeed18.jpg

http://farm3.static.flickr.com/2308/2288059172_c48ca669fe.jpg

[Lazer]

Your picture is too large, our maximum image size allowed is 600px X 600px, can you take the time to reduce the size of your picture please.