The vehicles, sure. But they get orher, simple equipment too.
In the incredibly rare event you have an active terrorist attack and can move the MRAP to it before it's over, it may provide the benefit of movable cover.
The rest of the time you have to park it (in two parking spaces likely), train people with it, fuel it, clean it, maintain it. It's just a huge distraction that sends a terrible message to the people you are supposedly serving.
And what events in the US are at high risk of attack by IEDs and mines?
Also, a regular truck will not stand up to storm debris in strong winds.