whenever I read a paper about Maxwell equations or Magnetohydrodynamcis the boundary conditions for the magnetic and electric field are either given by ($n$ is the outer normal vector)
$B \cdot n = 0, $ $E\times n=0$ or
$B \times n = 0, $ $E\cdot n=0$.
Why is never e.g. the case $B=0$ on $\partial \Omega$ considered? Does it have physical reasons? That one can for example only measure the normal component? But why is then sometimes $B\times n=0$ given? Or does it have mathematical reasons. That e.g. the Maxwell's equations are not wellposed for $B=0$ on $\partial \Omega$.