I understand your point crumb-bum, regarding the fact that there are price swings in PTS price when a snapshot is announced. Yes some of us might be compelled to sell seeing the price rise and the possibility of making a profit.
On the other hand though, people need to know when a snapshot will happen. As it was cited before, the point for insider trading is significant. A lot of people would cry out for injustice and rightly so, knowing that a handful of people knew about the snapshot and have grabbed a whole bunch of cheap PTS just before snapshot. Giving that information out 2-3 weeks in advance gives everybody the same opportunity to do so.
Also, some people might not want to receive shares of one new DAC and prefer to take a reasonable profit on their PTS (selling high just before snapshot, buying low just after). Having it announced in advance make it possible.
There are several long term holders, but there are also several traders that make a profit using the normal price swings. Let's say they just sold a whole bunch before the snapshot without knowing it, they would be really frustrated to know that they missed the snapshot. Those kind of traders wouldn't like to trade PTS if this was the case. And these traders are necessary to have a healthy buy/sell order book and help with the liquidity of the exchanges.
Does my points make sense in your opinion?