There's actually no way to know if they actually keep their word but I believe it's just a marketing strategy. They may actually give to some customers as you said and I also believe they will give to their regulars. Casinos make a lot of money so giving out bonuses to their regulars shouldn't be an issue for them because that money is just peanuts compared to what they make daily.
But bonuses aren't money and shouldn't be considered that, they are just bonuses or you could say, are chances given to players so that they can try and win some money with it, if they fail, it's gone, and even if they succeed, there are certain conditions to be met before they can cash it out.
These bonuses don't just fall from the sky, folks. They're cuningly cooked up to tug at our heartstrings (and wallets). The sweet-talking offers, the sneaky fine print – it's all engineered for maximum psychological impact.
But even with all the mind-bending, who can resist the adrenaline rush of a bonus? Racing to meet the wagering demands or dreaming of that life-changing win, it's undeniable that bonuses give gambling that extra shot of pizzazz.