Why start a new journal just because the year rolled over? Genuinely asking.

I am curious about the reasons why people switch to a new journal every year even if they have a lot of pages still left in their current journal? What is the benefit of doing this other than knowing for a fact the dates contained within the book? I think I find cover to cover more satisfying than knowing there was still so much room for activities! Lol I'm just curious what you guys think and maybe offer reasons that would change my perspective. Thanks!