I think it might be the classic distinction between "simple" and "easy". I do believe that most of those problems are "simple" - typically when you read solutions, it's under 20 Python lines of code; and not really complex or difficult to understand code. At the same time, I agree it's not very "easy" to do them well (come up with a solution, code it up, test it, and explain everything along the way considering trade-offs and pros and cons) under the interview stress and time pressure. Even the most brilliant and well prepared people do fail them for a reason.