Multi-Vis Oils Less Lubricating?

Why is it aircraft engines specify a single weight oil, i.e., SAE 30, not
mult-vis oils? This is mysterious to me because aircraft engines must be
started under varying temperatures just the same as cars.

Once started and warmed up, automobile engines operate at a more constant
temperature than do aircraft engines. If operating temperature would be
the criterium, then car engines would be better served than airplane
engines, yet we see mult-vis the rule for autos, but single weight for
airplanes.

Could it be that the multi-vis additives somehow detract from the
lubricating qualities which are better in single weight oils? On the
contrary, could it be that most aircraft engines predate multi-vis oil and
were certified for the then available oils which were single weight? There
are multi-vis aircraft oils, so perhaps later engines were certified with
multi-vis oils and the argument of superior qualities does not apply.

Also, I wonder why aircraft multi-vis oils are labeled for aircraft but not
cars and vice versa. Isn't SAE 5W-30 the same whether it is poured into an
aircraft engine or a car engine? Why is aircraft oil specially labeled and
costs more than car engine oil?

 

Partly because it is an "ashless dispursent" oil, and partly because
it has to deal with high lead content. - among other things, like
paying for lawyers etc and the cost of "certification".