.....and don't forget that it's fun!
On a serious note, we as military aviators train as we mean to fight and, for helicopter crews, this means low flying. As already stated this means as low as 50ft agl by day, if flying a CAD(concealed approach & departure) there is no vertical height limit but a minimum of 10ft laterally. Although this appears to be dangerously low, IT ISN'T. This type of flying also prepares the crews for bad weather operations; not too many civvies will fly in what the military helicopter crew are expected to operate in - 100ft cloud base and 1km vis is no fun. Some of you out there may have seen mil helo's crossing under power cables, this is an essential skill if you consider the height of the wires with regard to the weather minima above.
I hope this has helped......