You season food to add flavour. Its not always salt n pepper though. Any herb/spice can be used to season a dish.
But the reasons for using salt , especially for meat is to help enhance the flavour. I put it on steaks to help draw the blood/moisture out but it also add to the flavour, noticeably so. I use Maldon sea salt rather than table salt, the flavour is delicate and the big flakes make a huge difference. If you use table salt don�t use much due to the strength of the flavour, you want to taste the effect of the salt with the food not the salt itself.
Pepper adds, well, peppery flavours (similar to using roquette or basil to season).
They are designed to compliment the food not over power it, if you don�t like pepper don�t order anything with pepper in the description, I doubt you�d notice the seasoning. I�ve not worked in a kitchen before but should imagine seasoning with s�n�p is done in advance?
Salt and pepper is added to more foods than you�d think, but if you really hate it eat Chinese (decent Chinese) or Japanese, in fact most oriental cooking doesn�t use salt and pepper, instead relying on soy sauces to add the salty taste properties (umami is the name of the savoury taste for soy/salt etc).
I never put salt on my meals, I�m not keen, but I do season with it. If people were so off put by their uses it wouldn�t still be a mainstay of cookery still.