You might as well turn these kind of arguments around and wonder why all these experts from all these companies and all these countries never predicted/foresaw and anticipated all the big problems the whole JSF project encountered, why did they chose so many other faulthy, severely underperforming or hideously expensive defense projects in the past.
Good point. Although the fact that said experts are, as Ken said, "well paid" might explain a lot.
By the way, if the experts were always right, a few months ago we'd have seen the Queen, the Kaiser, the Tsar and the Arch-Duke get together to commemorate the centenary of the Christmas Armistice that ended the European War of 1914...