Why don't cats get out of the way when we trip over them?
Your cat doesn't notice that you're distracted and that you don't know he's there. He wants to be close to you and thinks you're paying attention to him.
Think about it. The cat is short and close to the ground. Cats always see what's in front of them. They don't trip over things. It is rare for them not to pay attention to where they are going, if at all. They have no experience with walking upright without seeing what's right in front of them on the ground.
When you are standing or walking they only have access to your legs. They want to rub against you and walk with you. They are in no hurry to get anywhere. Taking a stroll around the house with a loved one is normal and desired behavior.
The responsibility to watch where you are in the house is all yours. If one of my cats is wrapping itself around my legs as I walk, I just pick it up, go where I want and put it down when I get there.