I don't think that is necesarily true - in the sense we generally understand the word.
The bookie has a lot of bets going at any time, some of which will lose (most will lose most of the time) - but that is mainly due to the way the "Market" moves and the way we have been taught to trade it !
And stupid "Wisdom" like " A bird in the hand is worth two in the bush" and "Nobody ever went bust taking a Small profit" - Well in this game they are BOTH wrong !
A roulette wheel is random - the market moves in ways which are complicated and some think of as "Random" - but with a roulette wheel 50% of the time you win say the same amount as you stake (betting on black) - except for if it hits a Zero or 00 That is the casino's edge.
The bookie takes his "Spread" - whether you win or lose, but you will see the market jump up for two or three bars - sometimes a lot more. What do you do in those circumstances ?
Now you need to read the babypips school and set up and trade a "Demo account". Treat it like a computer game and learn it's tricks and devices until you recognise some of them - that then can be "YOUR EDGE" - Just always remember the market is Not neutral - if it was any silly sod could make money out of it - It doesn't matter whether it is "Rigged" or not - it will Feel like that !
Just bet against it until you can guess what it is going to do next, then you can learn to "trade WITH it !"