It's amazing how much is attributed to culture. What if I like more salt? European are not accustomed to ask for salt. What if the chef forgot to add salt? You'll wait till your food is cold. It's culture.
For ketchup, I'm afraid you'll need to stay in the US.
A chef forgetting to add salt sounds like a photographer forgetting to use a camera.
That’s a perfectly valid reason for complaining, then. Politely, of course, but the chef might use the feedback.
One thing is true though, I never ever had to add salt in restaurant in past 25 years, one can ask for pepper/olive oil/etc but salt? They often use too much of it to enhance taste ie in sauces. Maybe get your kidneys and heart checked with such refined palate.