Same here. I wear my Keen SPD sandals on the nice new hardwood floors and ceramic tile at my house with no issues whatsoever. They don't snag on carpet. But on the driveway/sidewalk, it's crunch time.
The only thing I can offer is that the concrete texture matters. The really smooth concrete factory floors at my workplace don't crunch, but the sidewalks/driveway look like a floor broom was used to smooth it out. Micro pebbles, indeed.