[ff_]

There's also the thing that while modern keeled sailboats are able to sail well upwind, that is not the case for these classic vessels which have a much smaller/shallower keel, and have a lot of trouble upwind. So if the wind is not right and you're on a schedule then motoring is the only option.

[ianburrell]

The keel is a factor but bigger factor are the sails. Modern sailboats are fore-and-aft rigged which can sail closer to the wind. Gotheburg is square-rigged which can barely sail upwind.

Square-rigged allowed for more sail. It also worked better for larger ships since had lots of little sails instead of one big one.