Tip sharing with the support staff (bartenders, sommeliers, busboys, and barbacks) was done at every restaurant I’ve ever worked at. I’ve never worked in a place where tips were pooled and split evenly among the waitstaff, and I don’t know that I’d ever care to be a waitron in that type of place, though I suppose in places where you don’t have a dedicated server that would make sense. Since (in most of the United States) the wages for waitrons are actually significantly less than minimum wage, the bulk of their take-home pay is in tips, and good waitrons will work very hard for their 15%-20%, and will also reward the support staff that keeps them from having to waste time filling water glasses or clearing dishes.
I have never worked in, seen, or indeed heard of a restaurant where tips are shared with the kitchen crew. I’m not saying it doesn’t happen, but it’s far from the norm. I have seen a few instances where a patron will seek out the grill cook or sommelier for a kind word and a special tip, but these are the exception rather than the rule. Line cooks at good quality restaurants generally make significantly more than minimum wage, so tips are not a part of their normal compensation.