It depends on what kind of loot box. For cosmetics it's pretty random. When the game itself feels stale I want a new outfit to make it feel fresh.

For P2W it's a treat after I've been grinding freemium for a while. It's like opening a beer on Friday after work. I don't spend 10-20k a week but I do occasionally spend that amount on one game during its whole lifetime. However, that also means I've gotten thousands of hours of enjoyment out of it.

But yes, while I'm only a 1000x (1000x compared to someone who just pays $20 upfront) there are certainly people who are 1000000x and much bigger whales than me. I can't speak for them.