An old and not well-observed piece of advice is 'Chew each mouthful thirty-two times.' I don't know if the advice is linked to etiquette; counting while chewing is one way of insuring that the imperative not to speak with one's mouth full is observed. First of all, the listener might be sprayed with masticated food and secondly, one would lose count and have to start again.
Maybe it is a way of controlling appetite and diet; it takes some time for the brain to register that the stomach is full by which time the speedy eaters among us have probably already eaten too much. However, chewing every mouthful so many times tends to reduce the food to a tasteless mush. The gristly meat of long ago school meals required much chomping until courage could be called upon to swallow the unappetising bolus and hope summoned that it would continue its journey down the oesophagus to the stomach.
Some foods, mainly meats, lend themselves to concerted grinding between the molars and premolars. To swallow them insufficiently milled is to experience transient pain in the trachea and oesophagus as they are forced down. Other foodstuffs, like lettuce and tomatoes, are not sufficiently dense to allow much chewing.
Perhaps we do not obey the advice because we are too busy or, if we are in company, everyone else is impatiently waiting for dessert and we are embarrassed to delay them further. Truthfully, sitting with someone who is solidly, stolidly counting every chomp of the jaws is unattractive but mesmerising and though it is rude to stare we cannot avoid it. Comparisons with cows and sheep spring unbidden to mind and sudden giggles must be disguised as polite coughs.
Compromise, then. Take smaller mouthfuls and chew efficiently but not religiously and I'm sure digestion and figure will benefit.