Perhaps they just don't like fishing.
I abhor low life, bottom dwelling, pond scum. Sadly there are those out there that take someone elses belongings and justify doing so by saying "it's their fault - they shouldda had their stuff locked up". Or whatever the hell goes through their mind.
My boat stays on the trailer at the marina year round. I do remove the stereo, the GPS, keys, and the small "boat box" (which has only 2 screw drivers, an adjustible wrench, a knife, trash bags, paper charts, and 2 spare bottle openers/cork screws (
) and some other odds-n-ends after each outing, but I leave the 5 dock lines and all the PFD's, all the canvas, and some other small items on board all the time - though those things are all stored out of sight.
My biggest worry is someone stealing my props.