But is there any risk to you being in the path of least resistance? All your pipes are connected (to the ground) so why would the electricity not take the readily available metal path?
The risk of death of showering during a lightning storm could be the same as the risk of death going for a 15 mile drive[0].
A typical lightning bolt is about 300 million Volts and about 30,000 Amps. Since even the best-grounded home certainly can't sink 30,000 amps of current into the neutral-bonded earth bar, it has to go somewhere. It finds multiple paths, and the current is shared between them. There's also the conversion to heat in all those insufficient conductors, etc.
Electricity doesn't only take the path of least resistance, it takes all paths available in inverse proportion to their resistance (impedance really.)
And since the water and sewage systems are plumbing systems and not electrical systems, its highly likely they'd be at different electrical potentials in a strike.
