The way AoC is structured, the early questions are accessible to everyone, even brand new programmers and they become more difficult gradually. Making the questions more difficult or giving them tricky edge cases would reduce the number of people who could participate.

To get on the leader boards for the early questions is more a test of one's ability to work quickly and accurately than of one's problem solving skills. Machines will always excel there, so I think it makes sense to exclude them as tools.