FMX question

i've noticed on most FMX bikes, the riders have shortened the front fender and the rear fender. i was wondering how/why they do this....is it for pure looks or is there some reason behind it. do they just cut it off and smooth it up a bit? i saw a Cycra front fender made for SuperMoto and it's quite short. is there a rear fender shorter than stock also avail. ? thanks
-88

reference, heres the cycra fender:
http://us.st11.yimg.com/store1.yimg.com/I/yhst-2483094475615_1887_2844554