Because the Israelis understand the principle that barriers which are not combined with observations and direct fire are only an annoyance to the enemy. In other words, putting a ladder up against an Israeli fence gets you shot by an Israeli sniper.
RE: In other words, putting a ladder up against an Israeli fence gets you shot by an Israeli sniper.
AHA, Herein lies the big difference. Legislators in America and many other special interest groups are going to oppose that.