Without waxing philosophical on the subject, I believe it comes down to the integrity of the product. You want something that holds up to the highest standards from top to bottom.

If you're not going to tidy up with whole pixel values, then why even name the layers/groups in your source file? Why name the file anything other than Untitled1.psd?

It's about holding the quality of your work higher than the ultimate value the consumer will see it.