The voltage is low,12v, so it's not as apt to conduct through water as higher voltages will.
Mainly, incandescent bulbs blow because they are hot and hit cold water when backing the trailer in. More of a rapid expansion/contraction of disimilar materials thing than it is an electrical issue. The sockets, being copper or brass, will also corrode/oxidize.
If you're not living on the edge, you're taking up too much space!