It's funny to notice reading the posts here how this matter is being taken lightly: I just imagine what people would be writing here if the concerned airline was some of less prestige than SIA. For instance one from Africa, South America, some Korean or Chinese or even Air France.
There would be lots of gun firing!
IMHO, this is just a simply case of poor airmanship coupled with lots of complacency/negligence. No excuses, no empty blah blah blah...
It's simply not acceptable that a trained and experienced international crew with such an unprofessional attitude.