We have B/P get togethers on Sunday afternoons. 3 shots for a buck @ about 75 yards. The stakes are Braggin' rights for the round and ownership of the "expert marksman pin" for the week plus a fistful of bills. Invariably with all the lips flapping someone will:
A) Double Load
B) Forget the Powder Charge Altogther
C) Leave a Cleaning Swipe in the Breech and Load over it
C) Load Correctly but have an inkling they may have done A or B, C, or D
D) And for the flints, they have on occasion hang-fired not to set off the charge
When in doubt... remove the cap, wait some time and pull the ball/bullet. (Although I have seen double-loaded bullseyes shot using the tire trick.)
A good stiff range rod for the ensuing tug-of-war contest is the best solution notwithstanding simple concentration and less chatter.
Other reasons...Cleaning accesories as Roundball stated, a tape ring on the rod to insure consistant depth setting shot to shot, and avoidance of lube trails on the thimbles and barrels.
These may sound goofy to some, but if you shoot 50-100 shots in an afternoon, a range rod or two just adds easy convience in my humble opinion.