If you remove that then it would be pretty much similar as normal bookies and I think its kinda essential there because it gives some people incentives to bet as early as possible thus building up the prizepool as well. If everyone just waited till last minute to bet then the prizepool will be much smaller and it might not even be lucrative enough for people to join in that pool
That is part of the reason it's there. It also compensates for the fact that people who bet later have more information available to them that may affect the outcome, eg. a star playing getting injured.