They have been almost thoroughly desensitised, they are like robots, automata who don't recognise the significance of what they see, who don't think.
Some people say to me things like: "I don't know why you're surprised, we see it all the time. It's just a traditional dress. Would you react in the same way if you saw a nun?"
I usually reply that being used to something shouldn't lead to its blind acceptance. If I had lived in Nazi Germany I probably would have got used to seeing arms risen in the Heil Hitler salute, but I would have resisted considering it right.
The burkha is a symbol, just like a nun's habit is a symbol. But the former symbolises a doctrine - Islam - that brings out the very worst in people, while the latter symbolises a doctrine - Christianity - that, by making them altruistic and considerate, brings out the best in people.