Danny, I use a capo because some of the songs that I sing are in keys that I find difficult to play on the guitar - like Ab, Bb, Eb, Db etc. I'm not great at barring chords so it's easier for me to play in C for example and put a capo on fret 3, than to try to play in Eb without one (impossible for me). Some keys are easy on the guitar, some are very difficult for less competent players - this is where the capo comes in.