What I know is that gambling sites will like people to put more money on their account on the gambling site so that the gambling site can make money from their customers. Every business likes money as they want to grow.
Be it gambling sites like someone to get addicted or not, they officially do not like it. They have guides and articles for people that are getting addicted. The gambling sites also have self-exclusion.
Just because they made self exclusion available doesn't mean that they have the best interest of gamblers at heart, remember they everything is programmed against that gamblers to lose so definitely they aim to make more profit and the only way the make these profits is when gamblers are addicted, that is just how their business keeps on increasing. Although it's possible that they don't want people to get addicted but it's hard to believe