On the one hand, I'm thinking, they might want to see that you mean business and are applying to good schools. On the other hand, maybe putting the 10 top universities makes them think you are likely not going to go with them even if they send an offer, so they don't want to waste anybody's time with you.
Regarding the second option, I heard rumors that there's some coordination between the universities, with them talking to one another about who's accepting who so that they don't end up with 70% of the offers being rejected. Does anybody have any intel on that?