Do members of the fellowship always warn others that elves have superhuman vision?

Legolas is often asked to look far ahead and he obliges. I'm in the Twin Towers fifth paragraph of Helm's Deep and:

"Gandalf dropped back to where Legolas rode beside Eomer. 'You have the keen eyes of your fair kindred, Legolas,' he said; 'and they can tell a sparrow from a finch a leagje off. Tell me, can you see anything away yonder towards Isengard?"...

We know he can see far. Gandalf and Legolas know he can see far. It is never suggested that he has to 'activate' long vision. So to those who know, does the fellowship always stroke his ego a bit (or does JRR always remind the reader) when asking him to look far, or is Gandalf preparing Eomer here for an otherwise unbelievable feat?

I am on a re-read for the first time in nearly 10 years. It's taking a while because it's hard to steal time to read but its every bit as delightful as I remember. Any answers from more frequent flyers much appreciated.

UPDATE: well I certainly didn't expect the eyestalks, but thanks all for diving into in-world reasons, author's style, and more. Forth Redditorlinguists!