In what I've read about classical Greece - about Persian wars, Pelaponesian wars, Battle of Leuctra, Macedonia conquest...etc. - military discussion seems to be mostly about the Phalanx with a bit about cavalry. At some point, however, chariots we're a very important military advance. Why the decline (if any)? Did this decline take place elsewhere?
I would speculate that chariots weren't used as much on Greek turf due to their lack of maneuverability on hilly terrain. On the plains of Egypt they would have a deadly impact, but try to drag them though hills and orchards, let alone the mountains…
Persians did try to use cavalry, but even that proved to be ineffective, and possibly had cost them defeat at Marathon.