It's a good hobby that helps pass the time. Improving at it , or anything, gives great satisfaction. But also because it's fun, and the people are (usually) cool.
I thought being able to solve was fun so I learned and got into cubing. Improved until sub-20 then for some reason lost interest and now I'm a casual cuber.
Relieve stress, meet cool people, help me not overstudy by giving me something to look forward to, I like modding puzzles. Makes me really really cool on public transportation.