The game contributions for wagering are determined according to the overall randomness and risk of a game. Online slots are random games, and therefore usually contribute 100 per cent to bonus wagering - with some exceptions.
Other games, such as roulette, video poker or blackjack can be played with strategies that lower the overall the risk of the game. They make the outcome more predictable.
These types of casino games are likely to contribute much less to wagering requirements at most casinos. With regards to lowering the risk, remember, that low-risk betting at table games, or other strategies to lower the house edge or risk are not permitted.