It's not as if a customer will expect immediate response -
Oh but they do. I've literally been carrying plates and been 'hailed' with someone issuing a drink or food order at me with my hands full of plates or a tray of drinks, and very rarely do they take kindly to waiting until you've delivered that food and you have to stand there until they've finished, with someone else's food getting cold, to say you'll be back or send someone else over, to get eye rolls and huffing back.
Some people hail you on the way back which of course is pretty normal, but I may have to make 2 trips to the kitchen for that table I'm serving, and again the waiting or sending someone else isn't acceptable.
I've even been tapped on the shoulder while taking an order because they 'Just wanted some water'.
For every person that would prefer to not be disturbed and catch attention, there'll be more customers that complain they're not being asked if everything is ok, and saying no one came back to ask if they want more drinks.
That's why it's done that way in so many places, it's not going to suit everyone, of course it's not, but doing that is impossible. I've been asked not to disturb people once they've had food delivered, politely, and I've respected that (because I'm allowed to use my common sense) and they've called out 'When you've a minute', come over when I'm at the till or gone to the bar. All good as far as I'm concerned, if they're happy then I am. You can't expect something that works for the majority of customers to be changed because you don't like it unfortunately.