You shouldn't need them but people in the hot ass climates do. His question has been asked many a time by people down there who drive fast on the freeway. I would guess the aerodynamics of the front fascia push the air meant for the spoiler actually underneath it, or disturb it enough allowing it to not be picked up
Mods: ZZP stage 3, 2.9 pulley, prefab pcm, 60lbers, AEM gauges, KandN CAI, SPEC stage 3+, ZZP S3 heat exchanger
ZZP long tube header, Strut bar, ZZP rear mount, Progress rear sway bar, Redline Tuning hood struts freshly installed.