Switchback track arrangements are used on the prototype where there is no alternative -- typically due to limited space.
They are very rare on the prototype* but quite common on some model track plans. Switchbacks on the model are tempting because
our layouts are always proportionally more limited in length than in depth. A switchback arrangement serving multiple industries
on each "wing" appears to make better use of our limited space. But this type of switchback spur incurs operating penalties
that cause real railroads to avoid their use wherever possible.
Some designers rely extremely heavily on this type of track arrangement, but in my opinion this makes the resulting
layout look unrealistic and operate inflexibly.
To understand why the prototype avoids switchbacks of this type, here's a simple example similar to a trackplan published
in a recent magazine. Industry "A" on the left wing holds five cars, industry "B" on the right wing holds two.