Bicycle tire and rim sizing historically has been a confusing subject as each country had it's own standards. Even some manufacturers such as Schwinn had some oddball sizes.

I have worked on a friend's 1985 Raleigh Technium and it still came with 27" wheels, 630mm, so 27" wheels were still being put on some new bikes that late. I have also seen recommendations that for international trekking 27" tires are much easier to find in many remote areas than 700C. This might be a reason to fit them on even a new bike, depending on intended use.