Because there's no better excuse for not buying an SUV than a supercar that's down for Costco runs.
BMW's insistence on dumping cash into the painstaking creation of wagonized versions of the M5 is an effort that does not go without appreciation. It's sort of like how the F10 M5 came with an optional manual gearbox for most of its life despite the fact that no one bought it (shame), but the fact remains that there's a small niche corner of gearheads that can afford one and aren't afraid to plunk down the money necessary to put one in their garages.
BMW hasn't confirmed whether or not it'll actually build an M5 wagon yet, but thankfully X-Tomi Design has drawn up what it'll probably look like so we can get an advanced preview of it in case BMW goes through with it. If and when that becomes a reality, it's really anyone's guess as to whether or not it'll make it to America. The fact that BMW keeps the 5 Series Touring out of our borders means that outlook for an M5 Touring in the US doesn't look good, but solace can be found in the fact that the M5's arch rival has an AMG E63 S Estate that can be bought from dealerships in our 50 states. Who wouldn't want to compete with that? Especially when CEO egos are at stake.
Thankfully, X-Tomi probably didn't have much of a hard time drawing this up. With the BMW 5 Series Touring and M5 already out, merging the wagon body and the M5's functional but aggressive styling accents is all that has to be done to complete the job. The simplicity in this rendering is more reason for BMW to make an M5 Touring, if only because it wouldn't have much trouble making it a reality. Simply replacing the engine with the M5's twin-turbo 4.4-liter V8, adding the M xDrive hardware underneath, and including all the upgraded hardware like the M compound brakes and M active rear differential is all it would take. Would the M5 Touring sell well? We'd like to think so, but in all likelihood that probably won't be the case. Could we care less? Not really.