> must reserve

With the current implementation exposed to the end customer, yes, that's required. Reserving specific seats isn't fundamental to the constraint that some people want to sit together.

Plus, the current reservation system is predatory in its own right. When booking you're dumped into a page strongly suggesting you must choose a seat, and all available options cost more than the base ticket.

Well, any half decent operator will put you next to each other and the other half at least lets you select seats during the check-in process. If that 90% certainty is not enough for you... just reserve the seats. Yes, it'll cost money, because otherwise there won't be any seats to reserve as anyone will do it.