Originally Posted by
Necroticplague
Because it makes magic items a mundanity, like a phone or a computer. How many other stories have such throwaway, indistinct magic items as DnD? I know of only one such story, and that's because it's based off a video game, and the main character is a crafter (and the other characters react, universally, in astonishment at this ability).
Magic items and abilities are supposed to be something special and rare, not some interchangeable 'bonus I need because my class doesn't provide what I need'. If you absolutely need a magic item for your class to work, it's your fault for picking an incompetent class. The mage is fine casting because it's an ability that they alone possess. A generic magic item should not exist because there is nothing special about it.