system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come just keeping food/drinks in our mouth isn't satisfactory enjoyment wise?

Most of us are fortunate enough to not just eat/drink for survival, but also for enjoyment. We taste food and beverages the moment they enter our mouths, and we can taste/chew/feel texture/etc.. but still we dont quite feel satisfied until we actually swallow.

For example: no matter how much you enjoy your favorite drink, you cant just take one sip and keep it in your mouth forever.
gpt
If you hold food in your mouth, the experience changes. Potatoes chips get wet. Salt dissolves.  Carbohydrates turn sweet. Cold drinks get warm. Fizz leaves the soda. Smells lose intensity (due to saturation) So quite literally the taste changes if you hold it in your mouth. 

I’m not sure that holding something in your mouth is as unsatisfactory as it is awkward. You can’t talk, can’t eat more, and you have to fight your instinct to swallow.

You have a sensation of being full that comes in part from literally having a full stomach. But that is only part of it.  Satisfaction with a meal depends on many things.. such as cravings, nutrition, special body needs, individual preferences, the time since you last ate, dehydration/ thirst is a big one.

In short, swallowing is part of a a complete, satisfying experience.