I used QR codes to get data (usually text or URLs) onto my phone all the time. I've never once thought about using a 'ms mobile tag' instead. And I don't know anyone who has.
But if you saw an MS tag, or Mobile Tag, or ATT Tag would you say, "Screw that, where's the QR Tag?". Probably not. You'd just scan it too. No one really cares what the tag technology is as long as it works.
That's just the point: it doesn't just work. My phone has Zebra Crossing (Google's open-source barcode reader), which scans everything from UPCs to QR Codes to Data Matrix... but not Microsoft Tag or AT&T's mobile tag format. Given that I am not keen on the idea of installing three new apps for these various proprietary tag formats, it doesn't just work. Instead, I have to recognize it's in a non-standard format, find/download the right app, etc. That's a big pain for something that already works quite well.
It's a day for someone to add all three of the formats listed on that page to Zebra Crossing. Now people may not want to do it for political reasons, that's fine. But I have no empathy for that.