Riddles, puzzles etc will promote cheating by walkthroughs and people selling
information.
Repetitive and tedious tasks will promote cheating by roboting and ways to
circumvent "cool-down" times.

Now guess in which case the cheaters are easier to catch and also the coding
task is simpler?

My original point in earlier post was that there usually if something is hard,
it is intentionally so.

and that didn't come out the way I thought it would, let me rephrase:

If something is (too) hard, there usually is both a reason and a need why it
is so.
If something is boring, there is no reason why it should be, except the need
to keep it somehow "hard" even if you get the information on how to do it from
someone who has solved the problem the wizard wanted *YOU* to solve.