I'd be worried if my wife expected me to call more frequently than that because it would imply our relationship wasn't as solid as I thought it was. Also British.

To me a strong relationship is one that lasts across time and physical distance without constant attention. Obviously within limits. But if my wife expected me to call her everyday, or vice versa, I could only assume that there was an insecurity/neediness that hadn't been appropriately handled.

Maybe the other person enjoys being on the phone and hearing your voice.

The point is showing you're there for the person, giving them the opportunity to mention something that's on their mind. It's about showing a special sense of availability, contrary to the texting availability that you provide to anyone else on God's green earth that may have your phone number saved or written down somewhere.

texting isn't ideal because you might get a response in an hour, or two days, or the next minute.

there's a lot of value in being fully present for a social interaction: when you're on the phone and paying attention, it's typically a lot more engaging than the other person watching a video, texting 4 other people at the same time, or whatever else people do in between texts.