Yes, sure you can use it but you can ONLY make payments on that credit card via an Apple Product only. So, yes, its a way for people to get locked into the Apple ecosystem. LOL
Once you set automatic payment you are done or you probably can call in and pay. Also if someone isn't paying your statement balance in full then new credit card might not be the best idea
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And yes the entire goal of the apple card is the nice integration with apple products. If someone is applying for apple card to use without Apple products then I'm not sure what that person is doing. Even though you can use the apple card without an iPhone that's not what Apple wants obviously and they want you tied to Apple ecosystem. Any company with 2 cents of common sense will do the same. If the hardware sales get to a point where they have to expand it to android, they will do eventually. But that's not going to happen soon since iPhones still are in majority of pockets. That's one reason why they want to expand into services and establish that business as the hardware business flattens.
My point is I'm not tied to it since it's not my main credit card nor I just have only iPhone or android phone. I'm flexible and use both platforms all the time without any fanboy craziness usual people get into