Comparatively speaking, it takes a lot less ice to walk on, compared to snowmobiles, UTVs, cars, pickups, etc. Farther north, even medium duty trucks see some ice time. And every year, I hear about vehicles plunging through the ice, frequently near flowing water like river inlets. Where I grew up in MI's Lower Peninsula, walking on the lakes wasn't generally a problem, and snowmobile traffic was pretty frequent as well. Vehicles? Very uncommon. That's the difference having Lake Michigan up wind, it keeps the Lower Peninsula a good 5-10 degrees warmer in the winter, and that makes a pretty significant difference.