The long shots with the people talking not perfectly framed is part of the visual language of reality programmes over here. It reminds viewers that what they're watching is real life, not an episode of The Only Way Is Chelsea Shores. Probably another of the things that we do differently each side of the pond.
I've watched plenty of UK docu-reality programs and I've never noticed that. And IMO its completely unnecessary and add nothing to the program visually.
Big brother isn't presented over here as docu-reality though, while The Only Way Is Essex, Made In Chelsea and Geordie Shores are, despite being non-reality. The daily programmes are still produced in a "highlights of the live stream" style, where poor framing, picking up conversations halfway through and so on are all expected - to the point that it's done deliberately to differentiate it from the non-reality reality crap we also show over here.
It's a difference in style, that's all. You see the exact same visual language in the likes of I'm a celeb, or in the past hells kitchen, celebrity scissorhands, fame academy and even bits of the x factor.