As usual, everybody jumps up and down waving their arms criticizing because "they" don't see a role for it.
But just citing the fact that many police departments use the bucket of sand shows, imo. that it can provide a useful function. They have officers loading, unloading, checking clear, etc.... hundreds of times a day. That creates a lot of opportunities for malfunction or error. A simple bucket of sand and SOP adds another layer of protection.
The best safety is always between your ears.... yet people make mistakes every day. With firearms, mistakes can be fatal.
So, imo., layers of protection, and "procedures/rules/policies" that back each other up are very beneficial.
Even a simple, distilled litany such as the "four rules" have redundant elements.
Heck, if I checked the chamber clear, why the heck shouldn't I point the barrel at my kids head when I pull the trigger.
For many, there is absolutely no reason to ever pull the trigger inside their house. But if you work on guns, you may be pulling the trigger, on many different guns, in different states up repair, quite frequently. Of course you wouldn't pull the trigger on a loaded weapon. But having a bucket of sand by the bench and always pointing the weapon into the bucket when pulling the trigger just adds another layer of protection.
If firearms safety was so gosh darn simple (which in theory it is) why the heck do we have so many ND, shot a hole in the wall... my leg.... my whatever posts pop up on this board just about every week.
And then everbody chimes in and offers words of comfort to the "offender" and chides anyone who offers criticism by saying "it will happen to everyone eventually".
Personally..... It hasn't happened to me and I'll take any and all constructive actions that seem prudent to me to make sure it doesn't happen..... bucket of sand included.