You're drawing a connection that's not there. It's indeed not a coincidence, but just because both situations fit the definition of the word "user" (and "to use").
People use drugs, whether they're addicted or whether they're taking a one-off dose given to them by a doctor. They are a customer in that situation if they're buying the drug from somebody (illegal dealer, pharmacy), but they're a user whether they paid or not.
Likewise, someone is a customer if Apple's if they paid for, or are expected to pay in the future, a device or service. But they're a user regardless of whether they're using a phone they bought, or a service that's being provided for free.
People can use services provided by charities, they can use skis on a mountain... there's absolutely no negative connotation to its general definition, it just happens that some things people use are bad and some are good.
In my mind, “user” stated to take over when we started having web based services that were used by people, but they were the ones paying. For example, Google and Facebook. Both got paid through ads, so they advertisers were the customers. The “users” were just the eyeballs the advertisers wanted to reach. So, you had to make your service compelling enough for someone to use for long enough that they’d see enough ads to make it profitable to provide the service.
It’s more akin to talking about “viewers” or “viewership” when talking about more traditional media.
For Apple, they are generally looking to get paid by the ultimate consumer of the product. So to them, we are the customers.
Maybe I'm just old, but we've called ... users ... 'user' since Unix or before. Perhaps it is just because Unix was integral to my early computing experience that I see it that way.
I'm the (super-)user of my Linux PC. I have total ownership and control over it.
Arguably "customer" makes the business relation to the provider of a service/device clearer.
The term I hate with a burning passion is "consumer".
"customer" represents a two-sided relationship, and I do feel that "user" is kind of one-sided, but gives agency, a user will use a product for their own purposes, presumably to help them achieve some kind of goal. A "consumer" is completely passive, their main goal is to do what the company tells them to do. A customer can walk out of the relationship, a user might complain about problems they have with your product, but the consumer will simply continue consuming whatever you want them to consume.
The worst part though, they seem to be mostly correct in their assessment.