Babies move, and many babies seek the security of the wall of the incubator when they are left unwrapped, as is often the situation when a newborn needs the Isolette - remembering the security of the tightly binding womb they just left. That is why swaddling is so calming to babies.
Makes sense to me. When my son was 2-3 weeks old, he wriggled up to one end of the bassinet - startled me badly when I first woke up because from my angle the bassinet appeared empty.