The amount of bets is more important how much those bets are. The 65 million bets makes a lot more people to come in and join then the number. If you read somewhere that windice had wagered almost 650 bitcoins so far, would you really understand how big or small that is? You would need the number as well and get an average of how much people play and so forth which is really just not worth the marketing it sounds.
However, when windice tells you it hit 60 million then a week later its at 65 million then in another week its already at 70 million (we assume) then you know it is loved and everyone plays there. That is why for marketing purposes the number of bets wagered is much better.