The headline is more than a little misleading. According to the Columbia Journalism Review:
These planes are for an Air Force fleet that’s barely used by Congress—at least compared to the others who also use it. Over the last five years, 86 percent of the use of the private-plane fleet has been by the White House and the military. Just 14.5 percent has been congressional use.
Not to mention that the addition just may make financial sense. From the WSJ article, well after the disingenuous lede:
The House Appropriations Committee says the new purchases are designed to replace seven aging and more expensive business jets. The net impact is one additional plane owned by the federal government and a substantial increase in its passenger capacity.