Did you ever have to put aside a project to respond to the 15th revision request from a client? Being the professional you are, you'll keep working until your client will be satisfied. Yet, who has so much time?
Unlike many years ago, you can't just be satisfied to only meet your needs in today's web environment. Instead, you need to please two factors equally: the user and the Google robots ranking you. The question, however, is which one should you try to please first?