They’ve been in those seats for hours and the bartender never came to take their drink order!
But there are reasons:
1. Cats don’t carry cash and rarely have working credit cards;
2. Their idea of a tip is a disembowled vole;
3. Zeus is underage anyway.
And anyway, everyone knows cats can’t handle their liquor. One beer and they fall asleep right on the barstool. Heck, sometimes they don’t even need the beer. But, clearly, don’t tell them that. They’re annoyed as it is.