It was to show that people who are professional do or tend to do the same thing repetitively. 

Like when we used to play football my coach would say the defense will be more afraid of you when you will practice your best shot 10,000 times rather than practicing 10,000 different shots a single time.

The point is, Leon did not want to become like the character in that movie (or may be he wants to become) but as he was a professional he had a routine of doing things, which he followed strictly.