I think you would find the same phenomenon in any creative endeavor, be it writing or composing or coding. A work on any medium is an imperfect representation of how it exists in our minds, and any creator with the degree of perfectionism required to produce a great work would surely be dissatisfied with the result of any attempt to bring it to fruition.

How many times have you finished a program but known it could be better, if only you had more time? A little optimization here, some refactoring there... The necessities of producing actual works prevent us from ever giving them the degree of polish we feel they deserve.