Most people will be baited into registering into a casino and playing their games because they saw an offer of great prizes and bonuses but once they are done playing they will realize how they weren't able to fully maximize the prize or bonus they were promised in the first place. Either way, the casino already got whatever they wanted which is to get more people to register and play. The question of whether they will keep playing is a different conversation but getting people to play at your casino is result of a successful promotion.
If a newcomer has previously read the wagering requirements of the welcome bonus and is satisfied with the terms, then yes, such a gambler will certainly continue to play. For the rest of the newcomers, the bonus can be a disappointment because many gambling platforms indicate the wagering requirements either in barely noticeable places on the site, or write about it in small print.