How does included gratuity work at non-US locations where tipping is fairly customary but likely not included by the hotel for the waiter?

Asking specifically for Mexico, where the service culture certainly is used to receiving tips but the bills often do not include it (as it didn't at the breakfast restaurant). I feel like I should leave some pesos on the table, but I haven't been able to see anyone else doing so. Same question also for the club lounge where service has been very attentive.I am a newbie to these international lounges that are actually nice