This is going to be a bit of a rant, so hold onto your hats.
If you're wondering about the title, I mean exactly what I'm saying here. Yes, there are Pagans (and probably people who use other descriptors as well) who use magic without believing in it. And that's a problem, but not for the reasons you might think.
First of all, let me be clear: I don't care what anyone believes. I don't give a flip whether their beliefs match mine, overlap slightly with mine, or don't coincide with mine in any way. What I do care about is whether people end up doing harm because of what they do or don't believe and how that dovetails with what they practice.
Let me give you an example. I won't offer any names, but this actually happened to close friends of mine a number of years ago. A female friend had experienced a miscarriage or two and was concerned about being able to carry a baby to term. When she got pregnant again, a couple other friends got together and did a ritual for her, to help her hold onto the baby. It was a powerful ritual and it worked. No more miscarriages.
The problem was, the friends who did the ritual apparently thought the effect was purely psychological or something. In other words, they didn't believe in the actual magic they were practicing. So they didn't think it was necessary to remove the energy of that ritual when it was time for the baby to be born. The pregnant friend went well past her due date, to the point that the baby was being endangered. Her doctor administered multiple doses of pitocin over the course of several days and it finally took a dangerous amount of it to get labor started. Even then, labor was long and hard, as if the baby didn't want to come out.
Coincidence? The friends who did the ritual would say so, but I wouldn't. If you're going to do magic, then pay attention to the consequences, for there will always be some. The fact that we don't know how something works doesn't mean that it doesn't work, only that we don't understand it.
I'm reminded of the owners of several local metaphysical shops, who have all told me the same story multiple times, just in slightly varying versions. A customer comes into their shop, devastated at the loss of a romantic partner, and demands some sort of magical tool or ritual to make that partner come back. Typically in this sort of situation the shop owners will try to talk the customer out of that kind of magic because it's coercive and obviously the relationship was already on the rocks. But the customer will insist, and after more warnings, the shop owner will usually offer something simple like a seven-day candle that's been prepped for a love ritual. The customer will go home, light the candle and do whatever else the instructions say, with a great deal of fervor because of their emotional state, and they'll get results. Then, almost without fail, they'll be back in the shop a few days later, totally freaked out that their boyfriend/girlfriend/whatever has come back to them but the relationship doesn't have the spark it used to. Their partner came back but is just there, sort of as a placeholder, without really wanting to be there underneath it all, and the customer can sense that. So the customer will inevitably want to know how to break the spell - the spell they insisted on in the first place, and the one they probably didn't believe would actually work (many customers admitted to the shop owners that they didn't believe it was real - they just wanted something to make them feel better).
So here's the thing: All actions have consequences. The fact that you don't believe in something doesn't mean it's not real and doesn't work. If you're going to do magic of any sort, even if you don't believe in it (though I don't understand why you would do it if you don't believe in it), then follow your actions to their logical consequences and prepare for those consequences. Don't assume it's all in everyone's head, though that isn't necessarily any less real than a solid object, but that's another post. Expect that there will be results, possibly results you can't predict or control, and be ready to take responsibility for that.
In other words, as my grandmother used to say, you're a grownup. Act like it.