Kelly -
I said the same thing from 1994 until about 2 years ago.
cut paper with utility knife or scissor = 3 seconds
apply 4 pieces of tape - one on each each of edge of label 4 x 3 seconds = 12
vs
peel label off - its already die cut so knife or scissors is needed and stick on - 3 seconds
And labels have the advantage that entire surface is adhered to the box. Remember that USPS says not to tape over the barcodes, if you do SOME readers won't be able to read them and this can cause delay.
But the biggest reason is the look. It's customer first tangible impression of your shop. How do you feel when you sit down in a restaurant and the silverware isn't spotless?
I just mockedup the same package with tape vs. adhesive labels. Tape takes more time than I though. You can see what both packages look like. I posted a photo of them side by side on my website. Tape looks pretty low rent. Makes me even more sorry that I waited so long.
http://leedsradio.com/images/tapevslabels.JPG