I've fallen out of the habit lately, but I was hitting the 10k target for a while. I have a sedentary desk job. So chores and playing with my kid got me up to about 3k. Then I'd walk for an hour during lunch to get another ~7k steps. Walking for an hour every day is fairly substantial commitment. I mean, it felt worth it. As you said, it's a huge productivity boost. I'm probably more productive walking 1 hour and working 7, rather than working a sedentary 8. It's not always easy to make that time in your day though.
I added the backstory, because I'm not questioning the value of the habit. I'm just always curious how much time people are devoting to walking when they talk about 10k steps.
Assuming you take one step every second (3600 steps per hour), it will take slightly less than 3 hours. One step per second is very leisurely pace.