They were...and have been trying to join ST for a long time, but ST decided they were NOT Trashy enough to qualify! So, ST picked neighbouring Garuda instead, a carrier not long ago banned from flying into the EU.

Seriously though, in a recent interview the outgoing MD of SkyTrash said as much: that the existing ST carriers would only permit new carriers which brought value to their own position to join the alliance: http://www.airtransportnews.aero/pri...ysis.pl?id=980

How could MH, a carrier rated as superior to the existing ST carrriers [e.g Skytrax rating] bring value to them? There is a PhD thesis to the answer, but in short existing ST carriers saw MH as a threat.