LorD, you are right, trophies are cheap, but i fear more in the sense that they take few effort to be done...with a system like steam having the game integrated into itself it's like...one line, plus naming them and adding a picture...
However the question here ain't "a level or achievements", the question is more along the line of well..."achievements or we watch paint dry". It is an extra, giving you some additional aims. You don't need it, but it doesn't take much afford.

...you should be proud; it looks amezzin'!