I would say so.
How detrimental could it be if someone poured something very bad into the tank and you ran it without knowing.
Is is possible to blow the engine and have the warranty voided if you put something besides fuel into the gas tank (I don't know)
It would be extremely rare yes, but leave your house unlocked at night because no one has ever tried to break in and just assume well it's rare it's never going to happen to me?
I always lock my house at night...
Most dealerships give you locking lug nuts so people don't steal the rims, but for some reason they don't lock your spare tire. Getting your spare tire stolen is a lot eaysier then jacking up a pickup to remove wheels\rims but they didn't put proper security on that either.
When I bought my truck I didn't see if it included locking front and rear cab doors, because I damn well assumed it did. I would assume the gas tank would also lock, and the spare tire maybe (but that is an outside lock so I would say not providing a lock from the factory is fair even if it is dumb).
Personally i'm not going to bother with the lock on my gas tank because of where I live now. Where I lived years ago 5 miles way you best believe I would get a locking gas fill door, or cap.
Locking fill doors or caps or some kind should be include on every vehicle or at a bare minimum be an additional package.