The sound 'barrier' is a physical barrier to pass through. Thrust SSC did a superb job; well done to them. Nobody can ever take the record away from Andy Green: the first man to break the sound barrier on land (unlike Chuck Yeager who may not have been the first - https://skeptoid.com/episodes/4154).
Always remember the TV film of the Thrust SSC crew being asked "was it worth it" and then hearing the two sonic booms and a cheer.
1000mph is just some arbitrary speed. Admittedly a difficult one to break, but arbitrary all the same. May as well aim for 1000 nautical miles per hour, or 1000 Linguine per nanocentury (apologies for mixing measurement 'standards')