It's easy to forget that the only way the whole damn contraption (you + bike + Fredly gear + etc.) is connected to the road via the tires+rims is through the spokes -- those flimsy little things. The hubs don't hover on their own, they are held up by the spokes and all the forward/backward force of accelerating and braking is translated into lateral and rotational forces in the wheel that are transmitted through them, too.

Once that is in perspective, it should become a bit easier to ponder that lousy spoke tension just makes for a sloppy ride with wasted energy going everywhere, +/- causing problems in the spokes/wheel. The numbers that were kicked around here seem to be for a pretty sloppy wheel, YMMV, but they're not wacky.

Ever try running in soft beach sand, vs. hard sand (say at water's edge) vs. pavement? You won't be setting a personal best in the sand. Loose spokes on a bike are like soft sand for a runner. Until they break, then they're worse.