We know,generally, keto tautomeric is more stable corresponding enol.(please explain it apart from thermodynamic explanation)
Nitroso is analogous to keto form and oxime is analogous to enol form.
Then why oxime is more stable than nitroso?
In keto-enol tautomerism generally the keto tautomer is more stable than its enol counterpart because in the former a significant ionic character exists which stabilises it. However, there are certain special cases. For instance if the enol form is aromatic(phenol), or very bulky mesityl groups are attached, etc.
and in nitroso, nitrogen is attached to oxygen by a double bond.
Now it is known that greater the difference in the electronegativity values, stronger is the bond. This property makes the nitrogen carbon double bond stronger hence making oximes more stable than nitroso.
(electronegativity values: N=3.04, O=3.44, C=2.55)
I wonder if the $\alpha$ effect is in play here. Two hetero atoms with lone pairs bonded to each other have a weaker bond because of lone pair repulsion. This probably destabilizes the corresponding $\pi$ bond as well. That would favor the oxime.