Because all the earths combined would all the doplegangers be on the same earth like would there be more than one superman or flash on the same earth
Check out Flockers on Arrow & The Flash. arrow.wikia.com/d/u/44210964
No, we still have other Barry Allens. Such as Ezra Miller and they are still casting for both Wally and Barry over on Titans so that Earth clearly would still have a Barry Allen.