Why are fad diets so popular - yet we still lap up heavy SUVs?

I have had two 5 Series tourings, an XF Sportbrake, S-MAX, C-MAX and numerous SUVs (Disco 4, 5, Disco Sport, Freelander 2) as family wheels. Whilst the big estates with big diesel engines are great on the motorway and give you the odd tail-out smile, their rear seat roominess is surprisingly poor for 5-metre cars. The MPVs are cheap and cheerful, get the job done but are forgettable, unrewarding, unexciting transport. Land Rovers are awesome when conditions turn gnarly, but overkill for most people (wading depth, articulation, towing capacity all compromise other attributes like interior space and efficiency). Disco 5's row 2 seats are not particularly comfortable or roomy for taller teenagers (the seat is low to the floor so your knees are up in the air like an old XJ). The boot floor is also crazy high for a dog to jump in and out of every day. After a recent new family car search I was blown away by the interior of the latest Q7: genuinely spacious row 2 with a great seating position, beautifully finished, quiet, huge boot, tech galore... ticks all the boxes. Even better, it's available with large discounts yet has excellent residuals, so is comparable on price to large estates. I'm sure I'm going to attract the ire of Mr Walton with my choice, but it is genuinely the best car for my needs. Have you looked at Ford S-MAX finance deals recently? The residuals are so bad the monthlies are in the same league as large premium stuff even with a chunky deposit. Who on earth buys them? Seemingly no one as neither local Ford dealer had a single one to look at, new or used!