Most travellers do not. A very long lens is heavy, expensive, hard to stabilise and narrow in field of view, and keeping a fast subject inside the frame from a moving Zodiac is genuinely difficult. Wildlife also has a habit of approaching until a 600mm is far too tight.
Many of the classic Antarctic images are made at moderate focal lengths, because the landscape is part of the story. A penguin surrounded by its environment often says more than an extreme close-up of its head.
A moderate telephoto zoom you can hold comfortably and operate without a tripod is more useful to most people than the longest lens available.
Bring a super telephoto only if you already know how and why you use one. If you're asking whether you need it, that's usually your answer.