It messes up the handling of the bike when you lower it. It doesn't ride as well. I already crashed on the track BECAUSE my bike was lowered. I went into a left turn and my left peg caught the pavement and I high sided. I broke my collar bone, a rib and a finger as a result of it.
If you're a new rider and don't plan to take it to the track or do any sharp curves with it, just ride around for recreational or commuting purposes you should be fine.
Live your life so the the pastor won't have to lie at your funeral