system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 just why salt and pepper are added to so many recipes.

I've worked in kitchens for years, and adding a small amount of salt and/or pepper to a recipe is just part of the job now. But when I make a 5L soup (over 4hrs) and I'm using 20grams I really can't think it's changing the flavour much. 

Is it a chemical process? I know salt lowers the freezing temperature of water (proof: salting icey roads), does it have a simillar effect on boiling water? 

Is it for texture? Or for visual effect? Why does salt and pepper go in every recipe.
gpt
Holy shit! Table salt is amazing! It does two incredibly important things in cooking: 

1. It breaks down and releases sodium when it dissolves in your mouth. The sodium bonds to one of the major flavour receptors in your mouth (i.e. salty flavour). This has a synergistic effect on other foods; particularly savoury flavours (see point 2). 

2. It draws moisture out of foods, speeding up the caramelisation of sugars/carbohydrates in food. In food chemistry terms, these are called Malliard reactions. In ELI5 terms, it helps foods (particularly meats) brown and give that delicious seared flavour. These seared flavours activate other flavour receptors (particularly umami/savoury receptors, and sweetness receptors). It's like a sensory gang-bang in your mouth. 

Pepper contains glutamic acid (an umami/savoury flavour) and activates heat sensors in your mouth. It's like a bit of nitro for your taste buds.