sometimes I buy them just for fun. to test them out and all. Not all fake goods are bad, or rather, I wouldn't call them fake, they actually work anyway, the only problem is realiability. however, most of the time, their price is so low that you can get a few "fake" ones for the price of an original one

note: I'm not referring to all "fake" goods. Not trying to generalise anyway.
For instance, "fake" rechargeble batteries are definately a no no. If they leak, you risk damaging your electronic device or worst case, fire or explosion.