Why is that coding in job is so different from coding during college days ?

I have been in software job for almost 10-11 months and I strongly feel that what I loved in my college days has turned out be a completely different thing in job. I loved spending time before computer all day and I was happy solving coding puzzles and learning algorithms. I did some machine learning too and I really enjoyed my days .As soon as I moved into a job ,I don't find coding to be as fun as earlier it was .I remember that I was so much in love with it that I didn't do anything other than coding .During this ten months time ,I switched in order to overcome boredom and yeah salary issues too but I don't feel that fire. I don't find things to be fancy anymore .