If you type "normandie atlanticwall today" in in google maps, you'll find some well preserved items, like the grand bunker, there is even a V1 still there.
I think it is good enough and necessary to keep these places in good condition. Why keep all the stuff? If not the tax payer is going to pay for that, it could only been paid by donations.
http://maps.google.de/maps?hl=de&q=a...ed=0CDAQ_AUoAg