Thinking about the idea that the additional revenue helps reduce the pricing for all seats.
Perhaps this could be the case, but I have to wonder that AC may think oh we got X dollars from people paying for seat assignments lets reduce the price.
But if that is the case then indirectly we all benefit from the extra dollars for seat assignments, which means though we might also have to deal with the inconvenience when a problem occurs due to AC policy.
If you want a less stress experience without issues like this and families upset and seat switching then fly a mainline airline.
(Yes it does happen on main lines from time to time but far less frequently since they can select their seats when they buy. Just like I expect it happens pretty infrequently on AC international flights)