In many cultures, saying "thank you" or "goodbye" when leaving a gathering is considered a social norm and a sign of politeness and respect. It is a way of expressing gratitude for the time spent together and acknowledging the host or the people you were interacting with. The specific phrases or customs may vary depending on the culture, but the underlying principle of showing appreciation for the gathering remains universal.
In Western cultures, it is common to say "thank you" and "goodbye" when leaving a social gathering. For example, if you attended a party or a dinner at someone's house, it would be customary to express your thanks and bid farewell to the host and other guests before departing. Saying something like "Thank you for having me" or "It was great seeing you all. Goodbye!" would be appropriate.
In other cultures, there might be different phrases or gestures used to convey similar sentiments. For instance, in some cultures, people may bow, exchange specific phrases, or perform other customs when leaving a gathering.
Overall, the key is to be attentive to the social cues and norms of the specific culture or group you are interacting with. Being polite and showing appreciation when leaving a gathering is a way to leave a positive impression and maintain good social etiquette.