Because usually people (especially people that works with IT) trust computers. We trust webpages, we trust databases, we trust chat-bots and instant message apps. Now we created program that can't be trusted. Imagine that you using chat to send messages to your friend but 5% of messages are replaced by lie. Imaging working with DB where after each 100 queries one query will return wrong info. Usually its a people that makes mistakes. Now we have AI program that makes mistakes too.