It's not just for the practical purpose. Jan Tschichold writes: "Two constants reign over the proportions of a well made book: the hand and the eye." Indeed, large margins give a feeling of quality, luxury, and openness. Compare older books with spacious margins to tight ones in modern books so as much text can be crammed to save on printing.

Here's another reference about page margins: https://practicaltypography.com/page-margins.html

"The pleasure of reading an effectively designed document will soon outweigh the unfamiliarity of extra white space around the edges."