In the great scheme of things I could worry about, it’s pretty low on the list. Not that I spend any time worrying about anything, but still…
In the passenger cars and light trucks that most of us drive, the vehicle design includes, as several have pointed out, a locking cover for the gas cap, which is only (normally) opened from inside the vehicle’s cabin.
Since it is just a sheet metal cover and the lock is not at all “high security”, this can be easily bypassed or destroyed – in seconds – by someone who is determined to get at the filler nozzle. So it’s not as if there is “zero concern”; it’s not a highly secure situation.
On the other hand, my tires are worth nearly $100 apiece, and can be ruined if someone with a pair of diagonal cutters wants to clip off the nozzles – which would take even less time than fiddling with the fuel filler gauge. The windshield can be quite easily crazed, and the other winds even more easily broken. The sheet metal all over the surface of the car can be easily dented or punctured, and it doesn’t take a lot of force to rip off a bumper (even less to do it just halfway). Not to mention that anyone with a few minutes and access to YouTube can learn how to very simply and quickly open a locked car door with few or no tools, making all of the contents at risk. Aside from all of that, if someone wants to kill a driver, brake lines are easy to cut or puncture, and unless you know from experience, training or practice how to recover from “suddenly, no brakes” – or recognize the signs of decaying brake function, and take appropriate corrective action – then that’s a bigger potential problem, too.
And that’s just the car. Shall I tell you how easy it is to enter my garage?
If you think to yourself, “Well, now that I’ve got a locking fuel cap, all my security problems are solved!” then you haven’t thought much about the issue.