You're never burgled until you're burgled. So the people who leave their boats unlocked never have a problem until they have a problem.
Not wanting to make that transition ourselves, we have always kept our boat locked when we are not on board. There are no electronics on the flying bridge since we never operate from up there. We also keep smash-and-grab items like binoculars, cameras, iPads, phones, etc. out of sight when we leave the boat.
The other year I installed a latch plate over the gap between the main cabin door and the door frame to eliminate the risk of using a credit card or knife blade to push the deadbolt and door latch back. We have a clamp lock on the dingy motor and we lock the dinghy itself to the boat when we're not on it.
Our objective is not to deter the serious crooks as they will get into the boat one way or the other if they want to, but to cause the casual burglar to move on to an easier boat if he encounters our locked doors and locked dinghy and motor. From what we've been told over the years by our marina staff and local law enforcement, it's the casual burglar who is much more prevalent in marinas like ours. Kids, druggies looking for anything to sell, that sort of thing. And with hundreds of boats to chose from, they are much more likely to move on if they encounter even a slight inconvenience to breaking in.
We have insurance to cover losses but we don't want the hassle of having to go get new stuff, and insurance never quite covers the cost of replacement anyway since prices keep going up. So it's a hassle we'd just as soon avoid altogether.