Good table manners are important, but as pp have mentioned, there are different versions of what are good manners are dependent on some cultural influences. Dh is Spanish/Maltese with a huge extended family here in the UK. Mealtimes in his family are noisy affairs that would have appalled my straight laced, very middle class English grandparents who taught us no elbows on the table, don't talk with your mouthful, how to hold your cutlery, take your food to your mouth, not your mouth to the food and never lean across someone to reach for food. I've taught our dc the same rules, bar the elbows as that doesn't bother me at all.
Mealtimes for us are totally different to my childhood though, they're an occasion, even if it's just the 5 of us, because that's how dh and his family eat. If we're out to eat with the extended Spanish family it's noisy, chaotic and everyone talks at once and leans over each other to pass food around but I love it. It's way more relaxed and enjoyable than childhood meals at my grandparents.
I've taught my dc table manners because I don't want them to show themselves up when they eat at school, or friend's houses, at work or wherever, but I'm also pretty relaxed about talking, elbows on the table etc because we sit round the table to catch up with each other, as well as eat, so I want everyone to be comfortable.