Answer: After being NATO's cash cow for 75 years, Germany, France, Poland and other Euro countries knew that Uncle Stupid would pony up yet again so they wouldn't have to.
The following is copied from an article in the NY Times, link included.
“Gen. Dwight Eisenhower, NATO’s first supreme allied commander Europe, felt strongly that his mission was to get Europeans “back on their military feet” — not for American troops to become the permanent bodyguard for Brussels and Berlin.
“If in 10 years, all American troops stationed in Europe for national defense purposes have not been returned to the United States,” he wrote of NATO in 1951, “then this whole project will have failed.”
“But as leaders of NATO allies gather in Washington on Tuesday for the alliance’s 75th anniversary, some 90,000 U.S. troops are stationed in Germany, Italy, Britain and elsewhere, making up a significant portion of the 500,000 NATO troops on high readiness.”