Because that "meanwhile" takes years. There are still clients that use libX11 ("it works for them") instead of libxcb. libxcb was introduced in 2003. So "meanw

Because that "meanwhile" takes years. There are still clients that use libX11 ("it works for them") instead of libxcb. libxcb was introduced in 2003. So "meanwhile" you would have apps that are not DPI aware without flag, DPI aware without flag and DPI aware with flag. And even crappier desktop as you have now for years to come. The new API is not just for DPI; it is for many reasons, DPI is only one of the issues.