Not at all. You can ask for salt and or pepper. Now when you start to add things like whole seasonings and or things like ketchup on a steak, then that’s different. Some cooks go light on the salt or exclude pepper in meals because they are trying to please people with different palates or health issues. When I’m serving food to people who have to watch their salt intake, I pull back on the salt. Or people who can’t have pepper. So if it is reasonable to add salt or pepper to the dish, then I take no offense. But I knew someone who added a ton of ketchup and hot sauce to almost every meal and I found that offensive, even when I wasn’t the one who cooked. I actually told this person to just pour their hot sauce in a cup and drink that instead since ultimately that is all they are tasting.
So long as you don’t drown the food in salt, not a problem. I personally like to be able to add salt to my plate at the end of the day. You can add salt at any time. You can’t easily get rid of over-salted food.
Some people may get offended but a good host wants you to enjoy your meal and realizes that some people like their food a little bit saltier than others. I rather they do this than ask for something sweet or a lot of water because the food is too salty. Also a good host or hostess will always have the basics on the table. Salad dressing for salads, salt and pepper and any other condiments that usually would go with the dishes served. If its on the table than it is there to be used.