Probably the expectation that the ICO hype will be long gone and EOS will have to deal with real life expectations and the next-gen coin knocking on the 'attention-grabbing' door. It seems better to spread out in time your investment in this token.
Second, dont invest funds you cannot afford to lose. This ICO could be one where end price is 10x lower than in the first round.
You might be right on this, but the crypto world is always changing and more people start to adopt it. I don't see a reason why it should be 10x lower than in the first round.