My opinion is that it's a matter of etiquette and manners. If i go to a nice restaurant i most likely will think of the chef as an artist. Salt and pepper are usually on the table if i need them but if they aren't--and in a lot of high-end restaurants they aren't- i wouldn't ask for them, unless the food is really bland. In that case i would also let the server know to tell the chef. I wouldn't dream of asking for ketchup. I would never say anything to someone who did, but to me, it's like a man wearing a hat indoors (see i am so old-fashioned). Most people these days wouldn't even know or consider it rude for a man to keep his hat on indoors, but whatever--i value decorum and civility, lol.
I think restaurants where it is appropriate to use ketchup already have it on the table, or the server asks you striaght up if you would like it, A1 sauce, etc.
But that's just me. I am a throwback to another era. I also believe in giving up seats on the bus to the elderly and pregnant, so what do i know ?