OK, you asked what they usually do - and the answer is, series capacitor.
The Volume pot should be a large enough value, compared to the other impedances in the circuit - like pickup impedance and amplifier input impedance, that is has no appreciable effect when set to it's maximum. Most other impedances in the circuit are 10's of k (like the 50k input on a guitar amp), hence volume pots are 250k or 500k. Being an order of magnitude bigger, it's effect should be small. So small, that the small loss is swamped by variations in gain in all sorts of other places in the guitar pedals and amplifier.
A series pot would indeed let 100% through at full volume, but it would have another serious problem. At zero, there would still be some sound because it cannot have infinite impedance. In fact, for a 500k pot into a 50k amp input, you'd get approx. 10% of the signal voltage still coming through. The design decision is that it is better to be able to turn it all the way down.
good point in that last paragraph. it makes me wonder if theres a way to have the best of both worlds. i'll get to drawing for now