First a comment on the transparency - SQ does a lot better than most on their own website, so I don't understand the criticism there (I think Emirates are the best now in this regard - you select a fare and it tells you how many miles you earn). On many airlines - be they star alliance, oneworld, skyteam or unaligned - you have to find the booking code, then look through T&C or eligibily table to find out if it earns ... and as for booking through travel agents website, don't get me started .

On the issue around SQ fare earning or not earning points - well I guess they can get away as they position themselves as a premium brand. At a personal level, I have now lived in Singapore for 12 months, and have not used them for a single flight paid out of my own pocket. I have travelled 6 times to Australia last year, and on each occassion SQ was the most expensive of the three airlines, AND on their (lowest) fares did not offer points ($400-600 return on Emirates with Skywards miles, $700-800 on QF with QFF points, $800-900 on SQ with NO KF miles). It was really easy to NOT choose SQ. But they get away because many people here simply would not comtemplate flying anyone else.

Thai and Cathay are also quite restrictive in this regard, not sure about others.

As an addendum to this to illustrate how SQ command premium pricing, I just checked pricing for some travel in May for SIN-MEL return, and SQ's best fare does earn points. The comparison - Emirates $759, Qantas $908, SQ $1156. I will never understand how they command such premiums, - their economy product is (was?) good but not that good - but they do.