I'm not so sure that it's unintentional or silly - especially when approached from the other direction.
Consider a wizard and a cleric working together on a scroll of Cure Light Wounds. The wizard - who knows how to scribe scrolls - is providing one prereq, while the cleric - who knows CLW - is providing another.
When the cleric is designated as the creator, the scroll is divine, and the cleric can use it, or hand it off to his druid, advanced ranger, or advanced paladin friend.
When the wizard is designated as the creator, the scroll is arcane, and therefore not useful at all to the cleric. Similarly, it's not useful at all to the wizard, who doesn't have the spell on his class spell list. So, what do you do with an arcane scroll of CLW? Why, you hand it to the bard, of course, who is an arcane caster with CLW on his class spell list.
Similarly, the spell silence appears as both arcane and divine (Clr 2 and Brd 2). There's also Freedom of Movement - again, Bard and Cleric, but also Assassin (arcane) and Druid, Luck, and Ranger (divine).