E-commerce is a much bigger industry and unlike the casino industry which is often shunned for its existence the former is always welcome into every household. You cant compare these two, one is like a necessity while the other is a guilty pleasure.

So indeed they are not the most profitable but they are profitable, considering the number of players who regularly lose at the casinos and keep coming back to make money even more often. Being a part of the casino is hence profitable too, be their employee and you have a day job at hand. Be their investors and you are having a passive income.