Real world cruising altitude

[Becks]

I have been using a mobile app called 'flight aware' and have been watching flights all around the world. I noticed that on numerous flights, for example San Fran to Manila, (12.5 hour flight), that a Boeing 777-300ER would file a cruising altitude of FL330. I'm not an aviation expert obviously, but wouldn't a long haul flight like this be better geared for FL380 - 410?

[SamTDS]

It is all down to the Airways, a lot of the time the flight plan has altitiude changes making the altitiude graph look like a staircase