You are right. Most of the bonuses actually will reduce your chance to win. They make it attractive to confuse people with marketing and things. Some sites do have worth while ones but most just stretch your playing time and are often the same as the free giveaways just in higher amounts. Still... If you have good luck and a high bonus multipler on the deposit then you must reach the wage limit and of you do it means you have plays a lot and most likely will have won a lot since you forced to play that long. So its go big or go home with those promotions.