The problem is that when you start stacking connectors on a single stud you start loosing the integrity of the screw and resistance = heat is usually the product. The NFPA, National Fire Prevention Association code calls for no more than 4 conductors, grounded or ungrounded upon any one battery terminal. I personally like to keep it <2.
The other issue is disconnect ability. E-11 and good prudence calls for all ungrounded conductors to be afforded disconnect. The only exception being auto bilge and stereo memory.
Again the issue is heat and fire.
Think of this way, if you have a component, any component be it a starter motor, alternator stereo amp, blender, marital aid.... whatever go to short and start burning wires would you like to throw a Perko and kill it or try to get those wing nuts off? Time moves in a hurry when shizz is burning. Sometimes fuses don't work as well one would hope. I ve seen bait and bilge pumps catch on fire (as in FIRE) with rated fuses installed.
The other benefit is knowing the boat is dead. Kill the mains and the boat is dead except for a fused bilge pump.
You millage and opinion may differ.
With Blue Seas ACR's and Power Poles it's too easy to do do it right.