A couple of things. Simply having the gun on safe isn’t going to prevent an accidental discharge if you drop the gun or take a tumble. In certain cases, even having intercepting Sears won’t prevent a discharge. If you’ve actually had any time whatsoever into the inner workings of these vintage guns, you know that there are very few safeties on vintage guns that totally disengage the firing mechanism, aka completely isolate it. Stalking safeties and various manual blocking systems obviously being an exception.
Many vintage guns intercepting safety systems flat out don’t work. Various causes, for example weak or broken intercepting sear springs, poor design, wear, etc. One of the most common, especially on boxlock designs is sometime in the guns life, the intercepting safety system was totally removed (on both sides or maybe just on the problem side).
Muzzle control in conjunction with keeping your fingers off the trigger(s) are more reliable than any safety mechanism.
Having a mechanically sound gun (action in tune, maintenance done correctly etc) are also very important. Not having a trigger or triggers that are set like a match rifle is another consideration. Trigger pulls of at least 4 lbs have always been considered good, lower than that, probably somewhat of a liability, especially if you take a hard fall and knock the sear & hammer out of bent. It gets easier for that to happen the lighter your trigger pull is.
How many of you have ever tested your intercepting sears for proper function? How many would even know how to do it? I’m betting very few.
Again, a gun in excellent mechanical condition, keeping your fingers outside of the trigger guard, muzzle control, safe handling, properly negotiating obstacles and using your head are much better methods of being safe than strictly relying on a safety.