while missiles can be built to have irregular routes, this is more important for missile-based defense. there, with the distances and speeds involved it will cause the interceptor to need to counter the irregularities, which will make it need to also be much more advanced. small changes in thrust however (at a later time - and thus higher speed) can cause only so much of a change.

but more importantly - light-based interception can be re-pointed much faster then a missile can change it's own course.