haven't you already got one? Or is this like a 'why do you need more than one guitar?' question? Because I do, dammit: because I do?
that is totally a why do you need more than one. Dogg i have two bikes. There is a formula it will hold true for guitars too: x = n+1 where x is the numbers of bikes you need n is the number you currently own. It can also be expressed as x = s-1 where s is the number of bikes at which you will be divorced/dumped/exorcised.