Still helps to keep things as close as possible.....one reason why the lower end of a SCAR is basically an AR. Other than a different bolt location, most of the user-end bits are the same. Same reason why the sight picture for irons used by the US military has not effectively changed since 1936. M1, M1 carbine, M14, to some degree the Thompson and M3 (still aperature sights) the M16, M16A1, A2, A4 and M4 along with the M249 and M240 and AT-4 all use the same iron sight picture. The M249 and M240 (same manufacturer) keep the bolt handle and safety in the same location for the same reason.