Why Don't Wands Break Down?

From the Turkey City Lexicon (an entertaining dictionary of writing terms which I've run into several times in the past, most recently via David Isaak's blog):

• AM/FM
  Engineer's term distinguishing the inevitable clunky real-world faultiness of "Actual Machines" from the power-fantasy techno-dreams of "Fucking Magic.

I'm pretty sure this bit of the lexicon refers to the habit of certain sci-fi books to feature Futuristic Technology that never fucks up, always acts perfectly. In essence, it's Magic.

But hey, why should Fucking Magic always work so perfectly, anyway? In fiction I've read, guns jam. Cars break down. Pipes get clogged, tires go flat, doors creak, metal rusts. But I can't remember the last time I read about a magic item suffering the effects of wear and tear. This is especially noticeable in Aar Pee Gees (role-playing games) that bother to implement the effects of slamming a sword into giant rats and creepy fucking monsters but work perfectly if you're using that sword to zap something with frost magic. Even if it's completely broken (unusable, in game terms). Magic mechanics are usually limited to 'mana' or 'magicka' bars; in other words, treating magic power like batteries. (Or, as in D&D, you get a limited number of 'spell slots'.)

Outside of the RPG world, in fiction, these limitations are usually ignored. Even the books based on D&D rarely if ever pay attention to 'spells per day'. (I admit I've not read many of these books, as they're often... well, terrible.)

In the world of books, the last time I remember seeing magic breakdown appear was the second Harry Potter book, where a character breaks his wand, and it spends the rest of the book making spells rebound, blowing bubbles and making someone barf slugs for a couple hours. But this wasn't wear and tear, note, it was the result of being snapped in half. I can't think of an instance where a wand stopped working because of, say, a faulty magic spark plug.

Now, sure, it would be a little silly if Sauron's One Ring ran out of battery power if worn too long, but what about the many, many modern fictive magic worlds that are less Epic and Mythic and more down-to-earth? Something to dump in the idea pool, at least...