The 24 hour rule came about because a number of W European posters (mainly Brits and NL based) started to do little else but post on this and similar threads.
New posts from the same people were coming up at 10 minute intervals at one point - this really meant that those outside W Europe, or with a life to lead outside of PPrune, unable to contribute. It then got worse as if you (say as OP) didn't answer them IMMEDIATELY you started to get hassled, PM'd and on a couple of occasions IIRC someone tried to declare the challenge closed because they had to wait 24 hours for an answer.
So we were given the 24 hour rule, and it was rigorously enforced. Some of the offenders flounced off, some were banned but the majority reformed.
The rule is not perfect - I for one would prefer that a correct answer can be accepted by the OP at any time but that the number of posts be limited (or say you can only make a single contribution on any thread each day but the Mods have spoken. And they check up quite often
Its not perfect but it's a lot more civilised