If you have an electronic tuner, why do you need to hear the guitar to tune it????

Good question, but I nearly always have to fine tune afterwards by ear. May seem daft but I always find I have to.

I just wanted to minimise the number of gadgets I have to plug in. I figured a single box with pre-amp, on/off switch and tuner would be neater than having lots of separate pedals etc. cabled together.