If your games are transparent and verifiably fair, you don't need to "make sure" that half your customers lose. You just post the payout odds, and have a fat enough wallet to cover the volatility. There is no "work" involved in deciding who wins or loses.

That said: If you're making a book (for sportsbetting) then yes, you are trying to balance the difference rather than predict a winner. That's a totally different thing from running a casino.