People who slip mostly just needs better shoes/tires, the difference between good and bad shoes/tires is huge. I have biked in Sweden during the winter, no problems at all, winter tires fixes most issues.
On the other hand, if I had a dollar for the number of times I bruised myself as a child I'd be a rich man.
Essentially it's about walking without ever putting your feet down such that they apply lateral force to the ground, however. Do that right, and it doesn't matter how slippery it is.
...and then you also can't apply force, so you can't walk. The hard part is to automatically test the ground you're standing on, ramping up the force fast enough to make progress, without thereby slipping. It's so automatic, I can't explain how or why it works. I suspect it's getting done in the spinal column, even.