“The U.S. Secret Service as of today will ban most trucks on an eight-block stretch of 17th Street NW just west of the White House because of the threat of potential truck bombs, D.C. and federal officials said.”

Washington Post

They’re lying to you.
My guess would be it’s the SS that is the one misleading. They already have a reputation for insane security precautions. And they currently have a president who demands more security than any in history.
The White House is already secure from any reasonable truck bombs. From t he front and back of the White House, you can approach no closer than the rough equivalent of 2 city blocks. And to each side are building so massive that they easily dwarf many times over the 300 unit apartment building in which I live. Buildings so large they would absorb the largest truck bombs I have ever seen.
They lie.
Now ask why.