Acero was always a lover of music, photography, and video games even before going to combat academy. When he eventually did go to Atlas Academy, he picked up weightlifting and boxing as something to do offset the fact that he hadn't mastered his weapon nor his semblance yet. But, even after doing that, he still wanted to keep his strength up, so those hobbies stuck around.
Mae also developed her hobbies before going to combat academy, but gardening, cooking, and going on walks through forest areas became harder because of dorms and school regulations. Mae goes to community garden to grow things, and will always sign up for school baking and cooking events. Going to the forest is hard and dangerous, as the only true forest around the school is the Emerald Forest, an initiation ground with a good amount of Grimm, but it doesn't really faze Mae, as she's grown up around Grimm her entire life.