Two reasons for me.
1. It makes them more endearing to my wife and family who are less than thrilled with them at times.
2. My breeders all get names which will be used for IDs for the hatchlings. For instance... Two of mine are a GHI female named Onyx and a male Pastel Clown named Homey. The female's shortened ID I keep on whatever tub she's in is O1 and the male's is H2 (I already have another that starts with H). Each of their hatchlings IDs will start with O1H2 so I can better track their genetics.