Why do so many +1 magical swords exist:
- They were much more powerful swords, but the enchantments have worn thin over the centuries.
- Many swords become enchanted through use or user. A warrior of minor renown will eventually find her sword acquires +1 effectiveness. A sword that has seen a hundred battles in a dozen hands might also become +1. Greater bloodshed or a more legendary wielder can contribute higher bonuses.
- In the Elder Wars, 5000 years ago mage-smiths were stamping these things out like hot-cakes for the rank and file. Things were different back then and the rapid sword-enchanting rituals of that age are now lost.
- Mages can temporarily enchant a weapon at +1, but every now and then the enchantment sticks and the sword stays +1 indefinitely.
- It's just the result of certain alchemical minerals infused in the coal or iron from which the sword was made.
- Weapons from the planes beyond, are often a physical extension of the creatures who wield them. So the captured sword of a celestial or earth elemental warrior has some portion of his power residing in it.
- Perfect enchantments rarely work on the first try. Not all failed weapon enchantments result in curses though. Some just end up as lesser weapons, a few +1 swords are included in the high cost of most other magic weapon smithing.
- The flesh of some creatures, orcs for instance, exude oils in their sweat which gradually dirty and pit the blades they carry, while paradoxically giving them extra bight against the armor and flesh of others.