I believe the issue is that while the spouse visa was granted, she ultimately decided that she did not want to live in the UK and hasn't moved over. (though I believe she did spend some time in the UK for a few weeks or months after the visa was initially granted?) However, she still would like to visit on a regular basis despite living in the US. And at the moment, her spouse visa is still valid, but other than visits to the UK, she hasn't actually "lived" here or established residency here, nor has any intention of doing so. For now, she is free to come and go as she pleases with her spouse visa - but without actually living here, may find it difficult to register with a GP or open a bank account.
Unfortunately, I don't think there's an easy way to address a situation where a couple wish to live in their own countries, but still visit each other and maintain a relationship. Both the US and UK require a period of continuous residency before granting permanent residency, and even then, permanent residency can be lost if not actually residing in the specified country. And in most instances, it will be hard to open bank accounts/register with health practices in a country where you aren't actually living in (regardless of probationary or permanent residency status). The way the system is, you can either move to the other country and set up residency and access these things, or just be a visitor and not access these things. Even UK citizens living abroad can't just pop back to the UK for some "free" NHS treatment every once in a while.
To clarify for people, registering with a GP or opening a bank account does not require permanent UK residence...but typically requires UK residence on a legal basis (work, spouse, student, and so on) which is usually evidenced by a recent piece of official mail sent to a UK address.