Because of Lady Bird Johnson, Texas as those wildflowers along many of the highways. Not many other states do it to the same extent.
I-99... the Glen Quagmire of interstate routes??
VDOT likes to plant them in the ROW at some interchanges (I-64 at Northampton Blvd in Norfolk comes to mind). I find that any natural beauty of them is countered by the presence of a "WILDFLOWERS - DO NOT MOW!" sign every 10 feet