Mortise and tenon joinery is your best insurance against glue joint failure due to poor gluing technique or differential expansion and contraction between the back panel of a box and the sides of the box.  It may also keep the box intact if it is dropped or knocked off the wall by playful grandchildren.  I tested this type of joint construction by dropping four different boxes three times each from a height of about five feet so that a corner of the box hit the concrete floor of my workshop.  Not once did a joint break during these tests.  In contrast, the boxes I make with simple butt joints (the type of joinery typically used by SV box makers) may survive a fall onto a floor with a plush carpet, but they will most likely crack or break completely at one or more corner joints if dropped onto a hard surface.