I still remember of a professor in my university who has written also an UML book. He said it will be the most important thing in your software career and you will use it nearly daily in your future as software engineer. I was sceptical because it was too much preaching for my taste. Turns out I was right.

20 years later: I used it very seldom and definitely NOT in my daily software development tasks. Actually the sequence diagrams were really the most useful of them all for me too.