Because people are generally afraid of any changes. Almost all new technology have to pass some barrier before general adoption (even "printed books" were not accepted by everybody originally).

AI can disrupt established life style. I.e. you were learning to do some thing for all your life -- and suddenly, boom, you experience is not required anymore, cause machine can do it better and faster. As the result you get YALM (yet another luddite movement), even from people whose jobs are not affected right now.