Why do authors take the time to give characters hobbies? I think the answer is obvious; because it gives the characters a sense of realness, and more than anything, as readers, we want to connect with the characters in books. Even if the hobby is not mentioned, it still needs to be known because it can affect the character(s) in a myriad of ways.
Here's one example. Let's imagine that a character has a hobby of shooting weapons. This would, in turn, give them knowledge on target sizes and/or distances; and what's need to hit the target or do the most amount of damage. This skill could then help the character to better judge the distances between moving vehicles; or how long a line of people is at the ticket gate. You might be thinking, "All that because the character shoots weapons as a hobby?"
Yes, absolutely! A character without this particular knowledge could be someone that wrecks their vehicle all the time or is impatient when standing in line. Just think how that direct opposition could cause some excellent friction with the more educated character?
Hobbies are fundamental in affecting a character in how they speak and how they react to whatever tragic situation they've been thrown into in the plotline. So, hobbies are vital to character development because just as our hobbies shape us, they also shape the characters we love to read about and immerse ourselves into their story. Next time you're creating a character, spend a little extra time on their hobbies and see where it takes you.