These binoculars, probably WWII, have individual eyepiece adjustments,
but NO universal adjustment.  Why is this?  Or, is there a universal
(both lenses adjustment)?  Advantages? Disadvantages (known)?

Here's an answer from a website called " a guide to selecting binoculars"
CENTRAL vs. INDIVIDUAL FOCUSING... 

Central Focusing binoculars are focused by a single knurled wheel. An
adjustable right eyepiece is provided for any difference between the
eyes. Because they are convenient to use, Central Focusing binoculars
are in the greatest demand today.

Individual Focusing binoculars are adjusted for each eye at the
eyepiece. Because they are more nearly moisture proof, simple, and
sturdy in construction, military services require individual focusing
on binoculars they procure. Mariners and sportsmen, who are the sole
user of a binocular, focus each eyepiece on infinity and either note
the setting on an eyepiece for later use or tape eyepieces in
position.