Perhaps it's because they've got even more Q-car status (and kudos) than the saloons; you can play at conventionality by stowing a couple of Labradors or the results of a Homebase binge in the boot, yet it will still out-accelerate anything the slow side of a Porsche 911.
Not altogether unsurprisingly, the M5 Touring is identical to the saloon in most crucial areas, so you still get the 500bhp V10 engine up front, still get the electronically controlled dampers, as well as the various gearbox and power settings that transform the M5 from a car that's eyebrow-raising to hair-raising.
To practical things first. The boot is a decent size on this M5 - 500 litres with the seats up is right on a par with the best in class, and to get those seats to fold flat you only need release a single lever on each side.
There's also a split and powered tailgate, spring-loaded luggage cover that slides back automatically when you open the boot and nifty straps down the side that compartmentalise the boot and stop your shopping sliding around too much.
You'd be advised to remove any groceries before attempting to exploit the full potential of this car or risk turning it into the world's most expensive blender. The Touring is 0.1 seconds slower than the saloon from 0-62mph, but you'll still get there in 4.8 seconds.
Grip levels remain good in the Touring, but the single most impressive thing about it is that you don't notice it's an estate. It doesn't feel like there's any extra weight hung out back, and there's no more wind noise than with the saloon version.
This isn't a small car, so it doesn't shrink around you as much as an M3 say, but you're still very much aware what the tarmac's doing beneath you.
The flipside of all this is that the criticisms with this car remain the same as the saloon. In itself, there's nothing wrong with the M5 in either version, it's more the fact of where we live. Because the simple truth is that the M5 isn't suited to Britain.
The engine really starts to wake up above 5,000rpm, but in all but the first two gears, you're in danger of losing your driving licence.
The chassis and lightning-quick gearchanges are also slightly irrelevant. This doesn't stop the BMW easily being a 16 out of 20, but it is mightily frustrating.