Earning interest is no longer a valid argument in 2017 as it was in say 1980. $1,000 sitting in a 2.25% CD will only earn $5.64 in interest in the three months earlier you would spend it to prepay. That's barely enough to cover a cup of coffee.
For many people, prepaying may also be a cash flow issue. If you have to wait until you have the funds, it may sell out before you can book it yourself. And if you put it on a credit card but don't have the money to pay for it right then, you
pay interest on that and it's a lot more than $5.64. Waiting on refunds may also be a cash flow issue for some people.
I don't want to prepay in advance - if I have concerns about having everything paid for before the cruise, I would simply put it aside and continue to earn my very small interest payment rather than give it to someone else. It's still
my $5.64. I see no reason to give my money to someone else before I have to even if I earn no interest on it (I'm an accountant - I don't pay my vendors early unless I get something in return like a discount and I have that same view personally). And I don't want to have to wait to get my money back if it gets cancelled due to weather or inability to dock.
Although I don't double-book anything or book anything that I don't ultimately plan to do, there have been times when there is a different excursion that I really want but it's full. I keep checking and, if it opens up, I cancel the first and book the second. If it didn't open up, I'd still do the original booking. I don't particularly want to have to pay for two and wait for the refund. It's not a case of not being able to afford to, it's just that it's
my money and they haven't rendered any service yet nor is it known if they will be able to. And, yes, I know that's the same situation as paying for the cruise itself in advance but there's a higher probability that they'll render that service than that they'll render the service for the excursion due to unforeseen things such as cancellation for lack of bookings, inability to dock, weather, closures, etc. (yes, I once again reveal my accounting bias here). Cruises have been cancelled but not nearly as frequently as excursions.
I would definitely pre-pay for certain things. I just hope that have a liberal and respectful cancellation policy if they do start the pre-pay.
If the point of having people pre-pay is to ensure that they don't hoard bookings, then having a liberal cancellation policy (if that means being able to cancel for any reason and get all your money back) kind of makes it a moot point IMO. You could pay for a number of things in advance that you don't intend to necessarily do and then cancel on a whim and get your money back as long as you have the cash/OBC float or a credit card. You could effectively hoard in the same way as you could now; you'd only have to worry about whether cash flow is an issue while waiting for a refund or if there would be credit card interest you wouldn't get back that you don't want to incur.
However, whatever they choose to do, it won't impact my planning, booking or scheduling in the least. I'll just grumble to myself for about 5 minutes and then book and pay for what I want if they change policy.