Going back to the Carnival Cruise thing, I never understood this...

[Posteritatis]

9. A combination of sea conditions and cruise ships just not being built for that

You can only tow ships of that size (or even anywhere near that size) with either pretty specialized ships or ships that were built with that sort of thing in mind (like some warships). Hauling on those scales means the hauler has to be able to physically withstand the strain and have enough engine power to do so. A typical cruise liner isn't going to have that excess power, and they're (relatively) fragile ships to boot.

Add rough seas and you end up with a situation where it was more likely that you'd get two damaged ships, on top of whatever injuries occurred when the tow line (or the part of one of the ships it was attached to) gave way.