Actually, shorter hair doesn't get in the way as much as longer hair. While you can tie longer hair up, you can also style your short hair up so it wouldn't be flying everywhere. Also, longer hair, even when tied up, become a hindrance for someone could snag it and pull you using your hair, or it could simply get tangled on something and pull you back or slow you down. Also, hair can get heavy, the longer it gets, so shorter hair = lighter head = less neck pain. While long hair are aesthetically pleasing, it's a hindrance in movement. Overall, cutting one's hair often symbolize personal transformation so it's pretty apt imagery~