It certainly wouldn't perfectly solve things but the further out a prediction is made the more risk there is that the outcome could change - even for someone with insider knowledge.

E.g. I've worked in businesses where an M&A has looked a nail on cert - as part of a small discreet team involved we were being readied for the announcement etc. only for it to stumble a few days before completion.

Obviously there are some markets/situations where a few extra days won't make a difference at all, but I could see how something like that would introduce more risk/uncertainty for those with insider knowledge.