They make advertisements on the internet only for the needs of their casino network so that more people know and play in their casinos or in online gambling. In my opinion, there is nothing wrong with this, but what is wrong is that there are people who play in casinos who do not have self-control so that they become addicted. If they can control themselves while playing, maybe it will minimize the harmful effects of gambling.
Advertising casinos is basically a marketing strategy that every other business employs to get traffic and increase their customers base because the larger the customer base the more profitable they definitely hope to be, it's left with the customers to choose how to react to the adverts.
Like you rightly said there's nothing wrong with the casinos advertising and there's also nothing wrong with the casinos themselves but the problems continually lays within the gamblers who react in a way that ends up detrimental to them, and that's why most casinos always advocate responsible gambling always on their platforms, gambling it's self if followed the way it aught to be , it's actually fun and not harmful but gamblers abuse it to their detriment because usually anything fun can definitely be addictive.