Dave, the reasoning behind not buying the RT tickets is just that, flexibility. The ferries aren't known for adhering to a strict schedule, to be diplomatic about it. You are usually best off showing up to the ferry dock and buying a ticket for the next boat to depart. If you bought your ticket in advance and the boat you bought the ticket for is broken or otherwise running behind, you are basically stuck waiting for that boat or buying a ticket on another ferry and eating the cost of the prepaid ticket. It's just not worth the $5 discount. YMMV, but I guess it worked well for you once getting a seat on a boat that might otherwise have been "full", so if it works for you, good. Above is why most don't buy the round trip though.