So the party fighter's magic sword, that he's spent about half his gold on, gets destroyed. Maybe by a blackguard, or a rust monster or a nightwalker or some such.
What happens after that? The PC's effectiveness has been greatly diminished. Does he get a new sword out of party funds? Do the other PCs give him a bigger share of loot until they all have similar magic item values again? Does the GM give him a shiny new sword? Or should he have relied on Greater Magic Weapon like the gish and the cleric?