Which is why you have to have that discussion with them and ask them to consider whether or not their work satisfaction comes from being challenged at work or not.
And while they may not be honest with you about that, in general there are many things that interviewing people are often not quite as honest with the interviewer as you might expect. A good example was a guy who said he was ok with commuting from Los Gatos to Redwood City and took the job, and then called up the Thursday before the Monday when he would have started to say he had taken a job for lower pay but was closer to home.
And while they may not be honest with you about that, in general there are many things that interviewing people are often not quite as honest with the interviewer as you might expect. A good example was a guy who said he was ok with commuting from Los Gatos to Redwood City and took the job, and then called up the Thursday before the Monday when he would have started to say he had taken a job for lower pay but was closer to home.