To clarify, as youve not understood the joke, nor read the comments. As far as I understand it, were you to start sailing at the first point, you never have to turn to arrive at the second. That’s why it’s “straight”. On the 2d plane you are completely correct however.
For proper and better informed explanations read the other comments :D
Because (in NL) you’re supposed to wear a full protective suit with padding and a helmet, or get a significantly worse ticket and potential loss of head/limb.