Suslin Rigidity conjecture states that motivic cohomology 
$$
H_{\mathcal{M}}^1(\operatorname{Spec}(F),\mathbb{Q}(n))
$$
of the field $F$ coincides with motivic cohomology for the subfield of constants $F_0$.

The fact that first motivic cohomology don’t change under pure transcendental extensions gives some evidence this conjecture.

**Question**: Does there exist a more conceptual reason for validity of this conjecture? Does it tell us something new about algebraic cycles (under assumption that Standard Conjectures hold)?