Many times, ATC vectors them into it. See my latest rant, above.
Flight Service has even let pilots file flight plans into airports currently in the restricted area and the poor pilots are paying the price for blundering into it with approval of ATC. You can't even fly out of one of these airports without a special background check and a special flight plan and transponder code.
Some pilots have even had their tickets suspended because of this ATC incompetency.