There is a strong probability in LE you may deploy a weapon in or from/around vehicles.
I also think there is less of a probability this weapon would be a carbine. Most of the times weapons get deployed like that it's the result of a pursuit. With how dynamically those situations end, the odds of deploying a carbine are low, non-existent if it's in the trunk.
I think there is a strong utility for magnifiers in LE, but there are trade offs there too.
I think the guys who work for smaller departments who are given more latitude in weapon selection are way ahead of the curve compared to large departments. Many times it seems big departments can't get out of their own way.

