So the real issue is weak restaurant management, not tardy customers. (Though not allowing separate bills always seems snotty to me.)
Nothing snotty about it, you have a party of 15 people and want to split the bill? Nope.
Its not worth it, it’s a waste of time and energy... As an owner of a restaurant I wouldn’t allow it, let alone the time and effort it adds to my staff.
Got 2 or 3 couples having dinner together and sharing a table, no problem, show up with 10 or 15 or 20 people, take up 2-3 tables and then want to split the check 17 ways to Sunday? nope. Not having my staff spend 20-30 minutes dealing with a group of folks trying to figure out how to split their bills, and arguing over, this wasn’t theirs, someone else ordered that, should be on their bill etc... Nope, 1 Bill.. you guys can figure out amongst yourselves how to pay it, not wasting my employees time on that nonsense. That time is better served serving other customers than making 10 trips to and from your table to split up your 1 check into the 17 slices you all now want.
1 Check, 18 or 20% mandatory gratuity and not seated until EVERYONE is present.
If that’s too much of a problem for your group, you are welcome to dine elsewhere.